National 

Transportation

Safety Board

Washington, D.C.

National Transportation

Safety Board

Washington, D.C. 20594

OFFICIAL BUSINESS

Penalty for Private Use, $300

PRSRT STD

Postage & Fees Paid

NTSB

Permit No. G-200

Highway Accident Report

Collision Between a Ford Dump Truck 

and Four Passenger Cars

Glen Rock, Pennsylvania

April 11, 2003

NTSB/HAR-06/01

PB2006-916201 National Transportation Safety Board

Notation 7743A 490 L’Enfant Plaza, S.W.

Adopted February 7, 2006 Washington, D.C. 20594
National Transportation Safety Board. 2006. Collision Between a Ford Dump Truck and Four 

Passenger Cars, Glen Rock, Pennsylvania, April 11, 2003. Highway Accident Report NTSB/HAR-06/01.

Washington, DC.

Abstract: About 3:36 p.m. on April 11, 2003, in the Borough of Glen Rock, Pennsylvania, a 1995 Ford 

dump truck owned and operated by Blossom Valley Farms, Inc., was traveling southbound on Church 

Street, a two-lane, two-way residential street with a steep downgrade, when the driver found that he was 

unable to stop the truck. The truck struck four passenger cars, which were stopped at the intersection of 

Church and Main Streets, and pushed them into the intersection. One of the vehicles struck three 

pedestrians (a 9-year-old boy, a 7-year-old boy, and a 7-year-old girl), who were on the sidewalk on the 

west side of Church Street. The truck continued across the intersection, through a gas station parking lot, 

and over a set of railroad tracks before coming to rest about 300 feet south of the intersection. As a result of 

the collision, the driver and an 11-year-old occupant of one of the passenger cars received fatal injuries, 

and the three pedestrians who were struck received minor-to-serious injuries. The six remaining passenger 

car occupants and the truck driver were not injured.

Major safety issues identified in this report include maintaining air brakes equipped with automatic slack 

adjusters, the knowledge and skills needed to drive air brake-equipped vehicles, and motor carrier 

oversight.

As a result of its investigation of this accident, the Safety Board makes safety recommendations to the 

Federal Motor Carrier Safety Administration, the 50 States and the District of Columbia, the Commercial 

Vehicle Safety Alliance, manufacturers and marketers of automatic slack adjusters, manufacturers of 

vehicles equipped with air brakes, the National Institute for Automotive Service Excellence (ASE), and 

publishers of ASE certification test study guides.

The National Transportation Safety Board is an independent Federal agency dedicated to promoting aviation, railroad, highway, marine, 

pipeline, and hazardous materials safety. Established in 1967, the agency is mandated by Congress through the Independent Safety Board 

Act of 1974 to investigate transportation accidents, determine the probable causes of the accidents, issue safety recommendations, study 

transportation safety issues, and evaluate the safety effectiveness of government agencies involved in transportation. The Safety Board 

makes public its actions and decisions through accident reports, safety studies, special investigation reports, safety recommendations, and 

statistical reviews.

Recent publications are available in their entirety on the Web at <http://www.ntsb.gov>. Other information about available publications also 

may be obtained from the Web site or by contacting:

National Transportation Safety Board

Records Management Division, CIO-40

490 L’Enfant Plaza, S.W.

Washington, D.C. 20594

(800) 877-6799 or (202) 314-6551

Safety Board publications may be purchased, by individual copy or by subscription, from the National Technical Information Service. To 

purchase this publication, order report number PB2006-916201 from:

National Technical Information Service

5285 Port Royal Road

Springfield, Virginia 22161

(800) 553-6847 or (703) 605-6000

The Independent Safety Board Act, as codified at 49 U.S.C. Section 1154(b), precludes the admission into evidence or use of Board reports 

related to an incident or accident in a civil action for damages resulting from a matter mentioned in the report. 
iii Highway Accident Report

Contents

Acronyms and Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

Factual Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

The Accident . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Narrative . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Emergency Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Injuries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Driver Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Truck Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Highway Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Motor Carrier Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Accident Truck Maintenance History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Motor Carrier Oversight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Inspection Selection System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Meteorological Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Toxicological Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Tests and Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Other Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Commercial Driver’s License . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Canadian Air Brake Endorsement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Brake Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Automatic Slack Adjusters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Brake Information in State Driver’s Manuals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Submission to the AAMVA for the Model Commercial Driver License Manual . . . 26

Commercial Vehicle Inspection Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Inspector and Mechanic Certification Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

American Trucking Associations Technology and Maintenance Council . . . . . . . . . . 29

Owner-Operator Independent Driver Association Survey . . . . . . . . . . . . . . . . . . . . . . . 29

Operation Air Brake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Commercial Vehicle Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

El Cerrito, California, Accident . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Other Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Exclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Accident Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Air Brakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Maintaining Air Brakes Equipped with Automatic Slack Adjusters . . . . . . . . . . . . . . 40

Knowledge and Skills Needed to Drive Air Brake-Equipped Vehicles . . . . . . . . . . . . 47
Contents iv Highway Accident Report

Motor Carrier Oversight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Blossom Valley . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Educating Motor Carriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

FMCSA Carrier Safety Rating Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Probable Cause . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Appendixes

A: Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

B: Results of Safety Board Computer Simulations of Accident Events . . . . . . . . 60

C: CVSA Pamphlet Air Brake Adjustment—Why is it so important? . . . . . . . . . . 61

D: Previous Safety Board Recommendations on Brake Adjustment 

and Inspection Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
v Highway Accident Report

Acronyms and Abbreviations

AAMVA American Association of Motor Vehicle Administrators

ABS antilock brake system

ADT average daily traffic

ASA automatic slack adjuster

ASE National Institute for Automotive Service Excellence

ATA American Trucking Associations, Inc.

Blossom Valley Blossom Valley Farms, Inc.

CCMTA Canadian Council of Motor Transport Administrators

CDL commercial driver’s license

CFR Code of Federal Regulations

CVSA Commercial Vehicle Safety Alliance

EDSMAC4 Engineering Dynamics Simulation Model of Automobile 

Collisions, 4th revision

FHWA Federal Highway Administration

FMCSA Federal Motor Carrier Safety Administration

FMCSRs Federal Motor Carrier Safety Regulations

GVWR gross vehicle weight rating

HVE Human, Vehicle, Environment

ISS-2 Inspection Selection System

MCMIS Federal Motor Carrier Management Information System

NHTSA National Highway Traffic Safety Administration

NPRM notice of proposed rulemaking

OOIDA Owner-Operator Independent Drivers Association 

PennDOT Pennsylvania Department of Transportation

psi pounds per square inch

SafeStat Safety Status Measurement System 

SIMON Simulation Model Non-linear

SRPD Southern Regional Police Department

THC tetrahydrocannabinol

UMTRI University of Michigan Transportation Research Institute

USDOT U.S. Department of Transportation
vi Highway Accident Report

Executive Summary

About 3:36 p.m., eastern daylight time, on April 11, 2003, in the Borough of Glen 

Rock, Pennsylvania, a 1995 Ford dump truck owned and operated by Blossom Valley 

Farms, Inc., was traveling southbound on Church Street, a two-lane, two-way residential 

street with a steep downgrade, when the driver found that he was unable to stop the truck. 

The truck struck four passenger cars, which were stopped at the intersection of Church and 

Main Streets, and pushed them into the intersection. One of the vehicles struck three 

pedestrians (a 9-year-old boy, a 7-year-old boy, and a 7-year-old girl), who were on the 

sidewalk on the west side of Church Street. The truck continued across the intersection, 

through a gas station parking lot, and over a set of railroad tracks before coming to rest 

about 300 feet south of the intersection. As a result of the collision, the driver and an 11-

year-old occupant of one of the passenger cars received fatal injuries, and the three 

pedestrians who were struck received minor-to-serious injuries. The six remaining 

passenger car occupants and the truck driver were not injured.

The National Transportation Safety Board determines that the probable cause of 

this accident was the lack of oversight by Blossom Valley Farms, Inc., which resulted in 

an untrained driver improperly operating an overloaded, air brake-equipped vehicle with 

inadequately maintained brakes. Contributing to the accident was the misdiagnosis of the 

truck’s underlying brake problems by mechanics involved with the truck’s maintenance; 

also contributing was a lack of readily available and accurate information about automatic 

slack adjusters and inadequate warnings about the safety problems caused by manually 

adjusting them.

During the investigation, the Safety Board identified the following major safety 

issues:

• Maintaining air brakes equipped with automatic slack adjusters,

• Knowledge and skills needed to drive air brake-equipped vehicles, and

• Motor carrier oversight.

As a result of this accident investigation, the Safety Board makes 

recommendations to the Federal Motor Carrier Safety Administration, the 50 States and 

the District of Columbia, the Commercial Vehicle Safety Alliance, manufacturers and 

marketers of automatic slack adjusters, manufacturers of vehicles equipped with air 

brakes, the National Institute for Automotive Service Excellence (ASE), and publishers of 

ASE certification test study guides.
1 Highway Accident Report

Factual Information

The Accident

Synopsis

About 3:36 p.m., eastern daylight time, on April 11, 2003, in the Borough of Glen 

Rock, Pennsylvania, a 1995 Ford dump truck owned and operated by Blossom Valley 

Farms, Inc., (see figure 1) was traveling southbound on Church Street, a two-lane, twoway residential street with a steep downgrade, when the driver found that he was unable to 

stop the truck. The truck struck four passenger cars, which were stopped at the intersection 

of Church and Main Streets, and pushed them into the intersection. One of the vehicles 

struck three pedestrians (a 9-year-old boy, a 7-year-old boy, and a 7-year-old girl), who 

were on the sidewalk on the west side of Church Street. The truck continued across the 

intersection, through a gas station parking lot, and over a set of railroad tracks before 

coming to rest about 300 feet south of the intersection. As a result of the collision, the 

driver and an 11-year-old occupant of one of the passenger cars received fatal injuries, and 

the three pedestrians who were struck received minor-to-serious injuries. The six 

remaining passenger car occupants and the truck driver were not injured.

Figure 1. Accident truck. (Source: Southern Regional Police Department)

Narrative

The 21-year-old accident truck driver worked for Blossom Valley Farms, Inc., 

(Blossom Valley) an agricultural nursery, making deliveries of landscaping materials, 

including mulch, dirt, and stone. He had been working for Blossom Valley for 10 days 
Factual Information 2 Highway Accident Report

when the accident occurred. According to the accident driver,1 on the day of the accident, 

he started work about 8:00 a.m., and his first delivery in the 1995 Ford dump truck 

consisted of 8 yards of mulch to an address in Parkton, Maryland. (See figure 2.) He also 

made his second and third deliveries, of 4 yards of mulch and 2 yards of Red Mountain 

Stone, respectively, to Parkton. On the way back from the third delivery, he stopped at a 

fast food restaurant in Shrewsbury, Pennsylvania, where he picked up food and then 

returned to Blossom Valley. He ate lunch in the truck while topsoil was loaded into the 

truck.2 The fourth delivery of the day was a load of 14 yards of unscreened topsoil, which 

was being delivered a day late. The driver indicated that he knew it should take three trips 

to complete the topsoil delivery because the truck’s capacity was limited to 5 scoops of 

wet topsoil3 (it was raining at the time). The employee who loaded the truck told the driver 

he had loaded 7 scoops4 and that the driver should go on with the delivery.

Figure 2. Map of the general region of the accident site.

0

0 10 km 

10 mile 

Shrewsbury 

Parkton 

Washington, D.C. 

Baltimore 

Philadelphia 

PENNSYLVANIA 

NEW JERSEY 

DELAWARE 

MARYLAND 

VIRGINIA 

Glen Rock 

York 

95

95

83

1 Southern Regional Police Department (SRPD) officers interviewed the accident driver on the day of 

the accident. A Safety Board investigator interviewed the accident driver on April 17, 2003.

2 The truck was loaded using a front-end loader that had a bucket or scoop that held about 1 yard of 

material by volume. Blossom Valley charged its customers by the yard; the company loaded by the scoop; 

and the weight of the scoop varied depending on the material.

3 A few days before the Glen Rock accident, the driver had a minor accident. At the time, the truck had 

been loaded with 7 scoops of unscreened topsoil. The driver said that when he told the owner about the 

minor accident, the owner told him that the truck should never be loaded with more than 5 scoops of topsoil.

4 The postaccident weight of the 7 scoops was about 11,060 pounds (5.53 tons), or about 1,580 pounds 

(0.79 ton) per scoop. Five scoops would have weighed about 7,900 pounds (3.95 tons).
Factual Information 3 Highway Accident Report

The driver indicated that he followed the directions printed on the delivery invoice 

given to him by his employer. He traveled north on the Susquehanna Trail and turned left 

on Church Street toward Glen Rock. He said he saw the “3/4 ton limit, Except Local 

Deliveries” signs at the beginning of Church Street but continued anyway because the 

directions given him by Blossom Valley told him to use that street and he thought he was 

making a local delivery. (See figures 3 and 4.) He said that he was traveling 25 to 35 mph 

on Church Street and stopped at the top of the hill near a water tower and electrical 

substation. (A witness following the truck indicated in a police interview that the accident 

truck did not stop.)

Figure 3. Map of the accident area, showing the Borough of Glen Rock (shaded area), 

the location of Blossom Valley Farms, and the intended delivery destination. The large 

arrows show the direction of the accident truck’s travel.

83 

616 

216 

216 

216 

Center Street 

Church Street 

Main Street 

0

0 1 km 

1 mile 

Blossom Valley Farms High Street 

Susquehanna Trail 

Delivery 

destination 
Figure 4. Weight prohibition signs at the beginning of Church Street. 

(Source: Pennsylvania Department of Transportation)

Factual Information 4 Highway Accident Report

The accident driver stated that as he started down the hill (see figure 5), he did not 

select a lower gear. He said that at some point during the descent, he pumped his brakes 

and the truck began to speed up. He also stated that about a quarter of the way down the 

hill, he lost his brakes and the brake warning light in the truck began to flash. He said he 

knew then that he had brake problems because his boss and a coworker had told him that if 

the brake light flashed, he did not have enough pressure [air pressure].5 He said he could 

not stop the truck, and he saw children and cars at the bottom of the hill. He indicated that 

he leaned out the window and yelled, “No brakes, get out of the way” as the truck neared 

Center Street (about 3 blocks from the accident site). He said he struck the back of a black 

car and thought he “went airborne.” He said that he did not sound the horn and that he was 

not wearing a seat belt. He stated that his recollection of the events after the initial impact 

was “vague.”

5 The truck was equipped with air brakes, which convert compressed air into a linear force that acts 

upon a number of components to apply the brake shoes against the brake drum, creating friction, which stops 

the vehicle.
Figure 5. Descending grade on southbound Church Street. 

(Source: Pennsylvania Department of Transportation)

Factual Information 5 Highway Accident Report

Witnesses reported that just before the accident, a school bus had unloaded students 

on Main Street. After exiting the bus, the students crossed Church Street and, as the bus began 

to leave, they walked up the sidewalk on the west side of Church Street. Witnesses also 

reported that four passenger cars were stopped at the “STOP” sign for southbound traffic on 

Church Street, where it intersects with Main Street. The first car in the queue was a 1997 

Pontiac Grand Prix, occupied by a driver and three passengers; the second was a 1996 Mazda 

Protégé, occupied by a driver; the third was a 1987 Chevrolet Nova, occupied by a driver and 

a front seat passenger; and the fourth was a 1993 Chevrolet Camaro, occupied by a driver.

About 107 feet north of the intersection, the accident truck struck the rear of the 

Camaro, causing it to rotate clockwise and pushing it into the Nova. The Nova rotated 

counterclockwise; the rear of the vehicle climbed the 6-inch-high curb and struck three 

children on the sidewalk and a metal post on a fence on the west side of the sidewalk. The 

Nova continued to rotate counterclockwise and struck the Mazda, pushing it forward into 

the rear of the Pontiac. The truck pushed the passenger cars into the intersection.

The Camaro came to rest near the northwest corner of the intersection of Church 

and Main Streets, facing south. The Nova came to rest with its front wheels on the 

southern sidewalk in front of the gas station, facing south. The Mazda and Pontiac came to 

rest in the parking area of the gas station, west of the Nova by about 25 feet and facing 

southeast. The accident truck proceeded across Main Street, through the western portion 

of the gas station parking lot, onto Water Street, across the railroad tracks, and then west 
Factual Information 6 Highway Accident Report

into an alley, coming to rest about 130 feet west of the intersection of the alley and Water 

Street. The truck traveled about 407 feet from its initial point of impact with the Camaro to 

its point of rest. (See figures 6 and 7.)

Figure 6. Intersection of Church Street and Main Street looking southbound on 

Church Street. (Source: Southern Regional Police Department)

Figure 7. At-rest positions of the vehicles at the accident scene.

Parking Lot

Gas Station CHURCH ST

MAIN ST Camaro

Nova Mazda

Pontiac

Truck

N
Factual Information 7 Highway Accident Report

Emergency Response

SRPD, Glen Rock Fire and Ambulance, and Loganville Fire Company responders

were dispatched at 3:36 p.m. Glen Rock Ambulance responders were on scene within a

minute, Glen Rock Fire Department personnel were on scene by 3:39 p.m., and SRPD

officers arrived on scene about 3:44 p.m. In addition, the Shrewsbury and New Freedom,

Pennsylvania, fire companies responded to the accident. Glen Rock, Rose Fire Company,

and Jacobus ambulance services transported patients to Penn State Hershey Medical

Center and York Hospital.

Injuries

The following table is based on the International Civil Aviation Organization’s

injury criteria, which the Safety Board uses in accident reports for all transportation modes.

Table 1. Injuries.

Driver Information

The 21-year-old truck driver lived in White Hall, Maryland, and had been working

for Blossom Valley as a truck driver since April 1, 2003. He possessed a Maryland Class

“C” noncommercial driver’s license. This license permitted the driver to operate an

automobile, station wagon, light truck, or any motor vehicle, except a motorcycle, with a

gross vehicle weight of 26,000 pounds or less.6

 A commercial driver’s license (CDL) is

required to drive a single vehicle weighing 26,001 pounds or more.7

Injury typeA Drivers Passengers Pedestrians Total

Fatal 1 1 02

Serious 0 0 11

Minor 0 0 22

None 4 2 06

Total 5 3 3 11

A Title 49 Code of Federal Regulations (CFR) 830.2 defines fatal injury as “any injury which results in

death within 30 days of the accident” and serious injury as “any injury which: (1) requires hospitalization

for more than 48 hours, commencing within 7 days from the date the injury was received; (2) results in a

fracture of any bone (except simple fractures of fingers, toes, or nose); (3) causes severe hemorrhages,

nerve, muscle, or tendon damage; (4) involves any internal organ; or (5) involves second- or thirddegree burns, or any burns affecting more than 5 percent of the body surface.”

6 Maryland Department of Transportation, Motor Vehicle Administration, Maryland Driver’s

Handbook (Glen Burnie, MD: Maryland Department of Transportation, September 1993).

7 Title 49 CFR 383.23 and 383.91.
Factual Information 8 Highway Accident Report

On the day of the accident, the driver was operating a commercial truck with a 

gross vehicle weight rating (GVWR)8 of 26,000 pounds that was equipped with an air 

brake system, which does not operate in the same way that hydraulic brake systems for 

automobiles do. (This report will discuss operation of air brake systems in a subsequent 

section.) According to the accident driver, he had no experience driving an air-braked 

truck before Blossom Valley hired him, and the largest vehicle he had previously driven 

was a pickup truck. According to the driver and his employer, he received no air brake 

training. He said that he had been shown how to operate the lift on the accident truck. At 

the time of the accident, he had been driving the accident truck for less than a week. 

Postaccident, he told investigators that he did not know that pumping an air brakeequipped truck’s brakes depleted the brakes’ air pressure.

Three days before the accident, on April 8, 2003, the driver had a minor accident in 

the same truck, which he stated was due to loss of braking. (The driver’s truck rolled into 

the back of a stopped passenger car. Neither vehicle suffered substantial damage.)

Truck Information

The accident truck was a 1995 Ford Motor Company, F-800 Series, 2-axle truck 

with a dump body. It was equipped with a Ford FD-1060 6-cylinder diesel engine that 

produced 175 horsepower at 2,500 rpm, an Allison model AT-545 4-speed automatic 

transmission, air brakes, and a hydraulic dump bed. It did not have an antilock brake 

system (ABS). The truck had an odometer reading of 145,095 miles. According to the 

manufacturer, the truck’s GVWR was 26,000 pounds. The SRPD weighed the truck during 

the postaccident investigation and found the total weight to be 26,600 pounds. In July 

2003, the Pennsylvania Department of Transportation (PennDOT) weighed the truck on 

portable scales with the load removed, and the empty weight was 15,540 pounds. The 

wheelbase was 207 inches, and the overall truck length was 25 feet, 5.5 inches.

The truck was equipped on the front and rear axles with standard S-cam drum 

foundation air brakes9 with automatic slack adjusters (ASAs). A Bendix model 2150 

single-cylinder, gear-driven compressor supplied air to the system. The air governor was a 

Bendix model D-2, permanently set at 110 pounds per square inch (psi).

As part of the Safety Board’s normal protocol, investigators tested the brakes 

postaccident. The diesel engine was operable, and all air testing was done with air 

supplied by the engine-mounted Bendix compressor, using the vehicle foot valve (brake 

pedal) for brake testing. The diesel engine was started and full brake applications were 

made at about 90 psi of air pressure. No air leaks were discovered in the air brake system. 

8 The GVWR is the value (based on axle ratings) specified by the manufacturer as the loaded weight of 

a single vehicle.

9 For the purposes of this report, the term “foundation brake system” (for cam-actuated brakes) means 

all mechanical components involved in providing braking force, including the brake chambers, S-cam and 

camshaft, brake drums, brake linings, slack adjusters, and all associated hardware, including washers, 

clevises, clevis pins, cotter pins, bushings, springs, and rollers.
Factual Information 9 Highway Accident Report

The brake testing results, summarized in table 2, indicated that the pushrod stroke for both

rear brakes exceeded the adjustment limit by 1/2 inch, resulting in little or no brake force

for the rear wheels.

Table 2. Accident truck brake test results summary.

The truck was equipped with Gunite10 ASAs on all four brakes. After the accident,

Safety Board investigators removed the automatic adjusters from the rear brakes, along with

the quick-connect clevises and clevis pins,11 and took them to the Gunite facility for testing.

The quick-connect clevises had wear in the clevis holes, where they attached to the slack

adjusters, and some flexing was observed where the two parts met. The combination of wear

in the clevis pin holes and flexing of the joints rendered the automatic feature of the ASAs

inoperative. When tested with the clevises and clevis pins from the accident truck, the

pushrod stroke would not go below 2 1/2 inches, at which point it produced little or no brake

force. When the two rear adjusters were tested at the Gunite facility with new clevises and

clevis pins, the adjusters worked correctly and kept the adjustment well under 2 inches.

All four brake drums were removed, examined, photographed, and measured. The

front axle had 15-inch drums and the rear axle had 16.5-inch drums. Heat cracks were

present in all the drums, and some discoloration (bluing) was found on the front drums,

which were smooth. The drum diameters were measured with a calibrated Central Tool

digital brake drum gauge, and all were within manufacturer’s tolerances. The brake shoe

widths were 4 inches for the front wheels and 7 inches for the rear wheels. The brake

shoes had no observable cracks and exhibited no anomalies. All the shoes were measured

and found to be within CVSA-established12 tolerances.13

Axle

Air chamber 

size

Slack arm 

lengthA

Pushrod 

stroke Adjustment limitB Rated strokeC

Left front T-16 5 1/2 in. 1 1/2 in. 1 3/4 in. 2 1/4 in.

Right front T-16 5 1/2 in. 1 1/2 in. 1 3/4 in. 2 1/4 in.

Left rear T-30 5 1/2 in. 2 1/2 in. 2 in. 2 1/2 in.

Right rear T-30 5 1/2 in. 2 1/2 in. 2 in. 2 1/2 in.

AThe distance from the center of the splined camshaft to the center of the clevis pin, which secures the pushrod to the

slack adjuster; also known as the “lever arm length.” B The maximum pushrod stroke permitted. The values utilized for the “brake adjustment limit” are those stated in the

Commercial Vehicle Safety Alliance (CVSA) North American Standard Out-of-Service Criteria. (Revised edition, April

2003.)

CThe total length the pushrod can travel inside the air chamber. (When the “pushrod stroke” is equivalent to the “rated

stroke,” generally no braking forces are obtained when the brakes are applied.)

10 Gunite Corporation of Rockford, Illinois, is a major manufacturer of wheel-end assemblies and

components for the heavy-duty truck industry.

11 The clevis and clevis pins connect the slack adjuster to the pushrod and are considered part of the

foundation brake system. A quick-connect clevis is a two-part clevis that can wear and flex.

12 The CVSA is a nonprofit organization dedicated to improving commercial vehicle safety that comprises

Federal, State, and Provincial government agencies and representatives from private industry in the United States,

Canada, and Mexico. The CVSA establishes and maintains commercial vehicle safety operational standards and

practices, inspection procedures, out-of-service criteria, and enforcement practices and penalties that provide for

uniformity, compatibility, and reciprocity among CVSA member jurisdictions and industry partners.

13 According to the CVSA North American Standard Out-of-Service Criteria, it is a violation for a lining

to be 1/4 inch (8/32 inch) below the wear indicator. (Revised edition, April 2003.)
Factual Information 10 Highway Accident Report

The truck was equipped with a dash-mounted red brake warning light, which 

illuminated when the air pressure went below 70 psi. An audible alarm accompanied this 

illumination. The spring brakes (parking brakes) were automatically fully applied on the 

rear axle when the system air reached about 40 psi. Investigators installed air gauges in all 

the air chambers, or in the service air line just outside the chamber, to check the amount of 

air going into the chamber during a service brake (foot pedal) application. When a forceful 

application was made at 90 psi, the chamber gauge pressure read about 75 psi on all four 

wheel positions (about 15 pounds less than the applied pressure).

The parking brake test was conducted by pulling the parking brake valve that applied 

the spring brakes. The engine was started and the transmission was moved into “DRIVE” in 

an attempt to move the vehicle forward on a concrete floor. The truck moved forward with 

only a slight increase in engine rpm. The truck was then placed in “REVERSE” and, with 

minimal engine acceleration, it went backward, even with the parking brake applied.

Highway Information

Church Street (State Route 3008) is a two-lane, two-way rural road 2.7 miles long 

between the Susquehanna Trail (State Route 3001) to the north and Main Street (State 

Route 216) to the south. The Susquehanna Trail is a two-lane, north/south roadway, which 

parallels Interstate Highway 83 on the west between Harrisburg and the 

Pennsylvania/Maryland State Line. The topography of the surrounding area is rolling hills.

As Church Street enters the Borough of Glen Rock, the downgrade becomes 

increasingly steep,14 from 3.4 percent near the top of the hill to 13 percent at the base of 

the hill (intersection with Main Street). According to PennDOT, the roadway width varies 

from 20 feet before entering the borough to 26 feet inside the borough. There is an 8-footwide parking lane on the west side of Church Street in the borough, next to housing, and 

the travel lanes are 9 feet wide. Solid, double, yellow lines separate the north/south lanes.

Main Street is a two-lane, two-way, east/west roadway traversing the Borough of 

Glen Rock. Immediately to the east of the intersection between Main Street and Church 

Street, a painted pedestrian crosswalk traverses Main Street. A gas station is located on the 

south side of the T-intersection of Church Street and Main Street.

The speed limit on Church Street traveling south from the Susquehanna Trail is 

55 mph. The speed limit changes 1.2 miles south of the intersection to 40 mph and again 1.8 

miles south of the intersection, as Church Street enters the Borough of Glen Rock, to 25 mph. 

The speed limit at the accident site (intersection of Church Street and Main Street) is 25 mph.

14 On June 10, 2003, Safety Board investigators measured the descending grade on Church Street using 

a surveyor’s transit at 32 points (every 50 feet) over a 3,300-foot distance to determine the grades on the 

roadway.
Factual Information 11 Highway Accident Report

According to PennDOT, the average daily traffic (ADT) on Church Street in 1998 

was 3,213, of which 8 percent was trucks and buses. In 2001, the ADT was 3,915, of 

which 9 percent was trucks and buses.

PennDOT data indicated that from January 1999 to December 2002, 11 traffic 

accidents occurred on Church Street within the Borough of Glen Rock. Of the 11 

accidents, 1 involved a fatality, 1 a major injury, 4 moderate injuries, and 5 minor injuries. 

Two of the 11 accidents involved trucks.

According to PennDOT, in 1965, after a fatal accident involving a truck at or near 

the April 11, 2003, accident intersection, the Borough of Glen Rock requested and 

obtained a weight restriction of 1,500 pounds (load capacity) on Church Street, and the 

street was so posted. At the intersection of the Susquehanna Trail and Church Street are 

R5-2 signs conforming to the Manual on Uniform Traffic Control Devices indicating that 

Church Street is a weight-restricted street. The signs indicate that the load weights are 

limited to 3/4 ton (1,500 pounds), except for local deliveries. The weight restriction 

applies only in the Borough of Glen Rock. (Refer to figures 3 and 4.) For traffic traveling 

northbound on the Susquehanna Trail, an additional sign reads, “Trucks over 1 ton use 

[Pennsylvania State Route] 216 to Glen Rock.” (See figure 8.)

Figure 8. Intersection of Susquehanna Trail and Church Street. Note the weight 

restriction sign directing trucks over 1 ton to use Pennsylvania State Route 216. 

(Source: Pennsylvania Department of Transportation)
Factual Information 12 Highway Accident Report

Additional signs and updated signs have periodically been erected in an effort to 

keep vehicles with weights in excess of the restriction from using Church Street. The 

borough ordinance15 reads (in part)

It shall be unlawful for any person to operate a motor vehicle, trailer, or semitrailer, as defined in The Vehicle Code, having a load capacity in excess of fifteen 

hundred (1,500) pounds, on Church Street ....[except] (a) Delivering goods or 

supplying services to any location on said street or accessible only by the use of 

said street; and (b) Moving any such vehicle to the residence of the owner of such 

vehicle or to the customary place of parking such vehicle at any location on said 

Street or accessible only by the use of said Street.

PennDOT officials indicated that the restriction applies to vehicles “having a load 

capacity” in excess of 1,500 pounds; many of today’s vehicles, including many pickup 

trucks, have a load-carrying capacity in excess of 1,500 pounds. According to PennDOT 

and the SRPD, enforcement of the weight restriction on Church Street is sporadic and 

complicated due to the wording of the ordinance and a local magistrate’s interpretation of 

the ordinance to allow use of this street for local deliveries to addresses that are not on or 

intersecting the street.

Motor Carrier Information

General

At the time of the accident, Blossom Valley was a private interstate carrier located in 

New Freedom, Pennsylvania.16 It was registered as a motor carrier with the U.S. Department 

of Transportation (USDOT). The carrier began operations in 1987; it transported building 

and construction materials, agricultural and farm supplies, and nursery stock. Blossom 

Valley trucks covered about 16,000 miles a year, including about 2,500 interstate miles. The 

majority of the interstate miles involved delivery of mulch, topsoil, stone, and nursery items. 

According to Blossom Valley’s owner, before the accident, he was unaware of many of the 

Federal regulations and requirements concerning motor carrier operations.

The Blossom Valley fleet consisted of five trucks—two straight trucks,17 a 1994 

Chevrolet dump truck, a 1995 Ford utility dump truck (the accident truck), and a 1990 

International18 truck tractor with a 1997 Reit flatbed semitrailer. The tractor-semitrailer 

combination truck was the only vehicle in the fleet that required a driver with a CDL. It 

had a combined GVWR of 80,000 pounds and, like the accident truck, was air brakeequipped. The Chevrolet dump truck was equipped with hydraulic brakes. The carrier 

15 Ordinance 150 of the Council of the Borough of Glen Rock, York County, Pennsylvania, August 4, 

1965.

16 According to the York Daily Record, “News Section,” for Tuesday, May 31, 2005, the business was 

sold in May 2005, and the new nursery does not make deliveries.

17 A straight truck is a single-unit truck with two or more axles.

18 International Truck and Engine Corporation of Warrenville, Illinois.
Factual Information 13 Highway Accident Report

employed two drivers, one with a CDL and one without (the accident driver). The driver 

with a CDL drove the two straight trucks and the tractor-semitrailer.

According to statements made during Safety Board interviews with the accident 

driver, the motor carrier owner, and the other driver, Blossom Valley did not give the 

accident driver a road test. Title 49 CFR 391.31–33, “Road test,” specifies that “a person 

shall not drive a commercial motor vehicle unless he/she has first successfully completed 

a road test and has been issued a certificate of driver’s road test....” Title 49 CFR 390.5 

defines a commercial motor vehicle as “any self-propelled motor vehicle... used on a 

highway in interstate commerce...[with] a gross vehicle weight rating of... 10,001 pounds 

or more....” The road test certificate or a copy of a valid CDL is to be retained in the 

driver’s qualification files.

The accident driver operated within a 100-mile radius of the home terminal and 

returned to that location every night, so, according to 49 CFR 395.1(e), he was not 

required to keep a record of duty status. However, as a motor carrier, Blossom Valley was 

required to maintain driver time records. After the accident, Blossom Valley was unable to 

provide investigators with the required time records. The accident driver’s actual hours of 

service are unknown.

On March 10, 2004, another Blossom Valley truck, driven by a different driver, 

was ticketed for traveling down Church Street, because the vehicle was in violation of the 

weight restriction.

Accident Truck Maintenance History

At the time of the accident, Blossom Valley did not have a regular, scheduled vehicle 

maintenance program in place as required by 49 CFR 396.3. Safety Board investigators 

obtained maintenance records from four facilities that serviced Blossom Valley’s vehicles: 

RG Group and Beasley Ford, both in York, Pennsylvania; Truck Specialties, Inc., in 

Shrewsbury, Pennsylvania; and C & T Transport in Parkton, Maryland. The service facilities 

did not have preventative maintenance agreements with Blossom Valley. Rather, they 

serviced the carrier’s vehicles when Blossom Valley brought them in for repairs.

Truck Specialties completed Pennsylvania State inspections of the accident truck 

in 2001 and 2002. The facility had last serviced the truck in May 2002 for non-brakerelated repairs.

On April 10, 2002, about 1 year before the accident, the accident truck was 

stopped in Maryland and subjected to a CVSA level 1 inspection,19 which included 

19 A CVSA level 1 inspection (North American Standard Inspection) includes examination of the 

driver’s license and medical examiner’s certificate and waiver, if applicable; the driver for alcohol and drug 

use; and the driver’s record of duty status, as required, and hours of service. With respect to the vehicle, it 

includes inspection of the seat belt, vehicle inspection report, brake system, coupling devices, exhaust 

system, frame, fuel system, turn signals, brake lamps, tail lamps, head lamps, lamps on projecting loads, 

loading procedures, steering mechanism, suspension, tires, van and open-top trailer bodies, wheels and rims, 

windshield wipers, and emergency exits (on buses). In addition, during a level 1 inspection, adherence to 

hazardous materials regulations is checked.
Factual Information 14 Highway Accident Report

checking the brakes for adjustment. At that time, the pushrod stroke for the left rear brake 

was 2 1/4 inches and the pushrod stroke for the right rear brake was 2 1/2 inches. The 

adjustment limit is 2 inches, so the brake condition resulted in the truck being placed out 

of service. Safety Board investigators interviewed the driver who was operating the truck 

at the time of this inspection. (Blossom Valley no longer employs this driver.) He stated 

that he [manually] adjusted the brakes before departing the inspection site. He also 

indicated he had adjusted the accident truck’s brakes three or four times during his 

seasonal employment with Blossom Valley during 2002. He further stated that he had 

worked full-time as a mechanic for a construction company, was a Pennsylvania Statecertified truck inspection mechanic, and had been a truck mechanic for more than 20 

years.

On January 20, 2003, the accident truck underwent a Pennsylvania State annual 

inspection performed by the Beasley Ford dealership in York, Pennsylvania. According to 

the service manager, the truck mechanics at Beasley are certified by the National Institute 

for Automotive Service Excellence (ASE). (For more information, see the section in this 

report on “Inspector and Mechanic Certification Requirements” under “Other 

Information.”) The dealership pays the expenses of acquiring and maintaining 

certification. The mechanic who performed the annual inspection was a Pennsylvania 

State-certified truck inspector. He told Safety Board investigators that the rear brakes were 

out of adjustment and that he had [manually] adjusted them.

According to the dealer’s service manager, ASAs, which work “pretty well,” still 

require inspection and manual adjustment, particularly if the vehicle operates in hilly or 

mountainous areas, or in dirt, gravel, or mud. The Ford owner’s manual for a year 2003 

model F650/750 (a vehicle similar to the accident truck) states

Inspect standard air brakes equipped with automatic slack adjusters for proper 

brake adjustment every 4 months or 20,000 miles, and more frequently if operated 

in hilly or mountainous regions or in mud.

At the time of the January 2003 inspection, the recorded mileage on the truck was 

142,810. The accident occurred less than 3 months later, at which time the odometer read 

145,095 miles. No manual adjustments are known to have been made to the brakes 

between the January 20 inspection and the April 11 accident. The truck had traveled a total 

of 2,285 miles during that period. Table 3 summarizes the inspection history of the 

accident truck, indicating the date of each inspection, the type of inspection performed, 

and whether the brakes were adjusted.
Factual Information 15 Highway Accident Report

Table 3. Glen Rock accident vehicle inspection history.

Motor Carrier Oversight

General

At the time of the accident, Blossom Valley had not undergone a Federal Motor

Carrier Safety Administration (FMCSA) compliance review or been assigned a safety

rating, so it was considered an unrated carrier. Because the carrier had been involved in

this multiple-fatality accident, the FMCSA conducted a compliance review of Blossom

Valley’s safety management controls on May 2, 2003. The compliance review revealed

discrepancies in the areas of drug/alcohol testing, driver qualification files, records of duty

status, vehicle inspection record-keeping, and driver/vehicle inspection reports. The

compliance review resulted in a safety rating of “Conditional”20 for Blossom Valley. As of

October 13, 2005, the FMCSA safety rating had not changed.

FMCSA standards require a motor carrier to have adequate management controls

in place to comply with applicable safety requirements. The FMCSA uses a rating formula

to determine a motor carrier’s safety fitness. The safety fitness rating methodology begins

with an FMCSA-conducted compliance review,21 applying the six factors shown in table 4

that rate the carrier’s compliance with the Federal Motor Carrier Safety Regulations

(FMCSRs).

Date Type of inspection Comments

August 2, 2001 Pennsylvania State annual Inspection and subsequent repairs

performed by Truck Specialties

mechanics; no brake problems noted

March 27, 2002 Pennsylvania State annual Inspection and subsequent repairs

performed by Truck Specialties

mechanics; no brake problems noted

April 10, 2002 Roadside, CVSA level 1 Placed out of service for out-ofadjustment brakes; driver adjusted

brakes and left inspection site

January 20, 2003 Pennsylvania State annual Inspection and subsequent repairs

performed by Beasley Ford; rear

brakes out of adjustment

April 15–18, 2003 Postaccident inspection (CVSA 

level 1)

Placed out of service for out-ofadjustment brakes, a loose brake

component, and an inoperative turn

signal 

20 A “Conditional” rating means a carrier does not have adequate safety management controls in place

to ensure compliance with the Safety Fitness Standards defined in 49 CFR Part 385, but the carrier is still

allowed to operate.

21 Title 49 CFR Part 385, appendix A.
Factual Information 16 Highway Accident Report

Table 4. Factors for FMCSA safety compliance and the results of Blossom Valley’s 

compliance review.

Factors 1–General, 2–Driver, 3–Operational, 4–Vehicle, and 5–Hazardous

Materials are rated “Satisfactory,” “Conditional,” or “Unsatisfactory.” Factor 6–Accident

is rated either “Satisfactory” or “Unsatisfactory”; a “Conditional” rating is not given. The

ratings are defined as follows:

• “Satisfactory”—Carrier has not violated any acute regulations or shown a

pattern of noncompliance with critical regulations for that factor.

• “Conditional”—Carrier has violated an acute regulation or had a pattern of

noncompliance with critical regulations.

• “Unsatisfactory”—Carrier has violated two or more acute regulations or has

patterns of noncompliance with two or more critical regulations.

After the FMCSA May 2003 compliance review, two other vehicles in Blossom

Valley’s fleet underwent roadside inspections and were placed out of service. (See table 5.)

Table 5. Other Blossom Valley vehicle inspections.

Inspection Selection System

The Inspection Selection System (ISS-2) is an FMCSA computer program

designed to assist the inspector in the field in selecting vehicles for inspection. The intent

of the program is to identify vehicles and carriers that have a history of unsafe practices

and poor safety performance. An ISS-2 inquiry provides three types of guidance

Factors Applicable FMCSRs and other 

criteria

Results of May 2, 2003, Blossom 

Valley compliance review

1–General Parts 387 and 390 Satisfactory

2–Driver Parts 382, 383, and 391 Satisfactory

3–Operational Parts 392 and 395 Satisfactory

4–Vehicle Parts 393 and 396 and out-ofservice rate

Unsatisfactory

5–Hazardous materials Parts 107, 171, 172, 173, 177, 

180, and 397

Not applicable 

6–Accident Recordable accident rate Satisfactory

Date Type of inspection Comments

June 3, 2003 Roadside Chevrolet pickup with a trailer:

trailer brakes inoperative (no

actuator switch); breakaway

brake device not connected;

vehicle placed out of service 

June 27, 2003 Roadside International tractor with Reit

trailer: 4 of 10 brakes out of

adjustment; vehicle placed out of

service
Factual Information 17 Highway Accident Report

(recommendations) to the inspector: “Inspect,” “Optional,” and “Pass.” (See table 6.) The

ISS-2 criteria are based on data analysis from the Federal Motor Carrier Management

Information System (MCMIS) and the Safety Status Measurement System (SafeStat)22

ratings in crash, vehicle, driver, and safety management history. If there is insufficient

information about the carrier in the SafeStat system, the ISS-2 inspection values are based

on the carrier’s size and number of past inspections.

Table 6. ISS-2 inspection values and recommendations.

When an inspector accesses the ISS-2 for a carrier, the system displays an

inspection value, as well as the source of the value. If the ISS-2 indicates insufficient data

to provide an inspection value, this means there is a lack of SafeStat or PRISM23 data on

that carrier. The ISS-2 also displays the carrier’s “Violation Details,” which provide

information about the carrier’s violation history compared to the national violationwarning threshold24 in specific categories. Carriers with a violation history greater than the

warning threshold are highlighted in that category, alerting the inspector to concentrate on

or pay particular attention to items in that category during the inspection process. An ISS2 inquiry also yields the latest MCMIS data (results of roadside inspections, compliance

reviews, and accident information) and carrier information, based on the most recent

updated carrier registration information.

As of March 24, 2003,25 Blossom Valley had an ISS-2 inspection value of 65,

based on insufficient data in the system regarding the carrier. As of September 19, 2003, 5

months after the accident, its inspection value was 82, based on the result of the FMCSA

compliance review safety rating of “Conditional.” As of September 23, 2005, the carrier’s

inspection value was 73. (The ISS-2 system automatically reduces the severity of an

infraction over time.)

22 The FMCSA’s SafeStat analysis program uses data from Federal and State sources, including

roadside inspections, accident data, and enforcement actions for all carriers, to develop a safety fitness

assessment for a motor carrier.

ISS-2 inspection value Recommendation 

75–100 Inspect (inspection warranted)

50–74 Optional (may be worth a look)

1–49 Pass (no inspection required)

23 PRISM is a Federal and State program that correlates motor carrier safety fitness to State commercial

vehicle registrations. See <www.fmcsa.dot.gov/factfigs/Prism.htm>.

24 This is an FMCSA algorithm that uses national inspection histories and carrier census information to

develop thresholds.

25 On May 24, 2003, investigators accessed the ISS-2 system to query the status of Blossom Valley. At

that time, the ISS-2 system stated that, as of March 24, 2003 (about 3 weeks before the accident), Blossom

Valley’s inspection value was 65.
Factual Information 18 Highway Accident Report

Meteorological Information

The nearest National Oceanic and Atmospheric Administration weather-reporting 

station to the accident site was the Automated Surface Observing System in York, 

Pennsylvania. At the time of the accident, the temperature was 45° F, the skies were 

overcast, and the winds were 7 knots from the west. There was a mist and light rain. 

According to SRPD investigators, the roadway was wet at the time of the accident.

Toxicological Information

The accident truck driver told police that he began using illicit drugs in October 

2002 (about 6 months before the accident). He acknowledged use of cocaine, marijuana, 

heroin, rock cocaine, and hydrocodone. (The driver did not have a prescription for the 

prescription medication hydrocodone.) He admitted using marijuana 2 days before the 

accident and estimated that he had last used cocaine about 2 weeks before the accident. He 

denied use of any controlled substance on the day of the accident.

Blood and urine specimens were collected from the driver at 6:33 p.m. and 6:55 p.m.,

respectively (about 3 and 3 1/4 hours postaccident). At the request of the York County, 

Pennsylvania, District Attorney, National Medical Services of Willow Grove, Pennsylvania, 

conducted postaccident toxicological testing of the truck driver’s blood and urine. 

Postaccident urinalysis showed the presence of methylecgonine and benzoylecgonine26

(both metabolites of cocaine), morphine,27 and Δ9-carboxy-tetrahydrocannabinol,28 an 

inactive metabolite of Δ9-tetrahydrocannabinol (THC, the active hallucinogenic compound 

in marijuana). Blood was tested only for THC and metabolites; test results were negative.29

Urinalysis testing results for ethyl alcohol and cocaethylene30 were also negative.

Tests and Research

To evaluate the effectiveness of the truck’s brakes, the Safety Board conducted 

computer simulations of the truck’s descent on Church Street to the accident site and its 

impact with the four passenger cars. Investigators used a Human, Vehicle, Environment 

(HVE)31 system that employed two physics modules, the Simulation Model Non-linear 

26 Benzoylecgonine, 4,900 nanog/mL.

27 Testing was positive for both total morphine (conjugated and unconjugated, 970 nanog/mL) and free 

morphine (unconjugated, 150 nanog/mL). Free morphine is the active biologic agent.

28 91 nanog/mL.

29 Laboratory reporting limits of >1.0 nanog/mL (Δ9

-THC) and >5.0 nanog/mL (11-hydroxy-Δ9-THC 

and Δ9

-carboxy-THC).

30 Cocaethylene is a compound formed when cocaine and alcohol are present simultaneously.

31 The Engineering Dynamics Corporation, Beaverton, Oregon, developed the HVE system for 

engineers and scientists to use as a simulation tool to study vehicle and occupant kinematics.
Factual Information 19 Highway Accident Report

(SIMON)32 for the truck descent and EDSMAC433 for the impact. The driver estimated his 

speed at the time of impact at 40 to 45 mph but stated that when he last looked at the 

speedometer, the truck was going 25 mph. The speed at impact was needed to determine a 

target speed for the truck at the bottom of the hill.

SIMON uses Brake Designer to assess the effects of temperature on the brake 

drums and linings. The HVE system has a Ford F-800 truck in its vehicle library. The size 

and adjustment of the brakes, the engine power curve, the transmission ratios, the 

differential ratio, and the load of the vehicle were set to replicate the accident truck in the 

simulation. Using the simulation tools, the brakes could be applied and released at 

different intervals as the vehicle descended the hill. SIMON does not model the 

compressor output and determine the available air pressure, but the force applied to the 

brake pedal can be varied. SIMON does model aerodynamic drag and rolling resistance. 

For the simulation, the downgrade was modeled as one grade that was 3,350 feet long at 

an average grade of 7.7 percent. This is equivalent to the grade at the accident site hill, 

which varied continuously. Based on the physical evidence (including tire marks and final 

vehicle positions) and HVE default vehicles for the 1993 Chevrolet Camaro, 1996 Mazda 

Protégé, 1987 Chevrolet Nova, and 1997 Pontiac Grand Prix, the EDSMAC4 simulations 

of the vehicle collisions near the intersection indicated that the speed of the truck at impact 

with the Camaro was about 35 mph.

The impact speed of 35 mph was used as a target for the SIMON downhill final 

speed. Witness statements concerning the speed of the truck on the hill varied. The driver 

stated that he stopped near the water tower and electrical substation at the top of the hill. 

He indicated that he pumped the brakes and that a quarter of the way down the hill, he lost 

the brakes. He said that as he was traveling about 25 mph, the brake warning light on the 

dashboard began to flash.34 A witness following the truck, however, stated that the truck 

did not stop and was traveling 25 to 30 mph at the top of the hill and then increased speed 

as it went down the hill. Numerous scenarios were simulated, including having the 

accident truck stop at the top of the hill and having it crest the hill at 25, 35, 45, and 55 

mph. Simulations were made with and without sufficient brake pressure, for a total of 35 

simulation runs. The simulations showed that the front brake drums could have heated 

from 615° F to 1,441° F. (At temperatures in excess of 900° F, brakes fade35 rapidly.) See 

appendix B for information on the simulations.

32 SIMON allows users to simulate the response of one or more vehicles to driver inputs and 

environmentally related factors. It is designed to fully utilize HVE Brake Designer, which models userdefined system components to estimate their behavior.

33 EDSMAC4, or the Engineering Dynamics Simulation Model of Automobile Collisions, 4th revision, 

permits simulation of single- or multiple-vehicle crashes and is based on the Simulation Model of 

Automobile Collisions, which Calspan developed for the National Highway Traffic Safety Administration 

(NHTSA).

34 Testing showed that the red brake warning light came on when the brake air pressure dropped below 

70 psi, and the rear parking brakes applied when the pressure dropped below 40 psi, but because the rear 

brakes were so far out of adjustment, the parking brakes would have had little or no effect on slowing the 

truck.

35 Brake fade is heating of the brake drums and linings, which causes an expansion of the drums, 

reducing a brake’s ability to slow or stop a vehicle.
Factual Information 20 Highway Accident Report

The simulations showed that if the driver had pumped the brakes rapidly and 

depleted the truck’s air pressure to below 50 psi, the truck would not have been able to 

stop. If the driver had applied the brakes too late on the descent, the front brakes would 

have overheated, and the driver would not have been able to stop. If the driver had allowed 

the speed of the truck to exceed 38 mph on the descent, the front brakes would have 

overheated and faded. The simulations showed that the lowest brake drum temperatures 

occurred when the brakes were continually snubbed36 on and off as the truck went down 

the hill. The simulations indicated that the front brakes would have slowed the truck 

somewhat, keeping the truck to about 35 mph at the time of impact.

Other Information

Commercial Driver’s License

The majority of States (32) have a classified license system, which is one in which 

the State issues different licenses for specific classes of vehicles. Before the CDL program 

was instituted (see below), in States that did not have a classified license system, any 

person licensed to drive an automobile could drive a commercial motor vehicle.

The CDL requirement was established under the Commercial Vehicle Safety Act 

of 1986 and became effective nationwide in 1992. It established testing and license 

requirements for drivers of commercial motor vehicles. The main purpose of the act was 

to reduce or prevent truck and bus accidents and fatalities by disqualifying unsafe 

commercial motor vehicle drivers.37 The classifications of CDL, by vehicle group 

descriptions, are

• Combination Vehicle (Group A)—Any combination of vehicles with a gross 

combination weight rating of 11,794 kilograms or more (26,001 pounds or 

more) provided the GVWR of the vehicle(s) being towed is in excess of 4,536 

kilograms (10,000 pounds).

• Heavy Straight Vehicle (Group B)—Any single vehicle with a GVWR of 

11,794 kilograms or more (26,001 pounds or more), or any such vehicle 

towing a vehicle not in excess of 4,536 kilograms (10,000 pounds) GVWR.

36 A 1992 University of Michigan Transportation Research Institute (UMTRI) study, conducted to 

determine what information should be included in the CDL program on braking a truck while descending 

mountain roads, found that it was better to apply more pressure (about 20 pounds) for 3 seconds and then 

release for about 6 seconds (a procedure called a “snub”) than to apply brakes at a low level of pressure (10 

pounds) and hold them on while descending the mountain. Snubbing resulted in slightly lower brake 

temperatures, and the hottest brakes were cooler if the snubbing strategy was used, but the difference was 

not large. See P. Fancher, C. Winkler, and M. Campbell, The Influence of Brake Strategy on Brake 

Temperatures in Mountain Descents, UMTRI-92-11, March 1992.

37 Title 49 CFR 383.91.
Factual Information 21 Highway Accident Report

• Small Vehicle (Group C)—Any single vehicle, or combination of vehicles, that 

meets neither the definition of Group A nor that of Group B as contained in 

this section, but that either is designed to transport 16 or more passengers 

including the driver, or is used in the transportation of materials found to be 

hazardous for the purposes of the Hazardous Materials Transportation Act and 

which require the motor vehicle to be placarded under the Hazardous Materials 

Regulations.

Any CDL driver operating a commercial motor vehicle equipped with air brakes 

must pass an air brake test indicating that the driver has specific knowledge about air 

brake systems, inspection of the brakes, and “implications of low air pressure warning.”38

If a CDL driver has not passed the air brake test, the CDL will display an “L” restriction, 

meaning the driver is prohibited from driving air brake-equipped vehicles. A CDL driver 

may have this restriction removed by passing a State air brake test at a later date.

Canadian Air Brake Endorsement

Since 2001, Transport Canada has required all drivers to have an air brake 

endorsement to drive any vehicle equipped with air brakes. According to the Canadian 

National Safety Code #4, “Classified Driver’s Licence Program,” a driver must possess a 

valid driver’s license of an appropriate class to operate the assigned vehicle, including an 

air brake endorsement when the vehicle is equipped with air brakes. Transport Canada 

reports that Canada has experienced a reduction in brake-related accidents since the 

adoption of this requirement.39 Also, between September 1999 and September 2004, 

Canada experienced a 25-percent reduction in brakes found to be out of adjustment to the 

point of being out of service.40

Brake Systems

Passenger cars are usually equipped with hydraulic brake systems. Trucks are 

equipped with either hydraulic brakes or air brakes. The two brake systems operate 

differently. A hydraulic brake system is filled with hydraulic fluid. When the brake pedal 

is depressed, a proportional force is applied to the fluid, which in turn forces the brake 

shoes against the drums, creating friction, which stops the vehicle. When the brake is 

released, the pressure is released, and the brakes release. Hydraulic brake systems are 

closed systems, so there is no depletion of the brake fluid. Also, hydraulic systems have 

little discernible lag time between pedal depression and brake application.

An air brake system converts compressed air into a linear force that acts upon a 

number of components, including the pushrod, slack adjuster, and camshaft, to apply the 

brake shoes against the brake drum, creating friction, which stops the vehicle. The 

38 Title 49 CFR 383.111(g).

39 This information was obtained through conversations between Transport Canada officials and Safety 

Board investigators during the April 2004 CVSA meeting in Little Rock, Arkansas.

40 From Operation Air Brake data for 1999 through 2004. (Operation Air Brake will be discussed later 

in this report.)
Factual Information 22 Highway Accident Report

compressor provides a supply of air to the holding tanks (also known as air supply 

reservoirs). When the brakes are applied, the stored air is distributed in the system through 

relay valves to the brake chambers, which convert the air pressure to a linear force. Using 

this force, the pushrod moves a slack adjuster that is attached to a camshaft, which rotates 

and causes the brake shoes to expand and contact the brake drum. When the brakes are 

released, the air used to activate the brakes is exhausted to the atmosphere. (See figure 9.)

Figure 9. Brake schematic.

Air chamber

Push rod

Slack adjuster

Brake lining moves 

outward when cam 

twists, contacting

brake drum Rotating cam

twists when 

brake is applied, 

spreading shoes

Shoes push linings 

against drum

Brake drum 

expands with heat

The air brake system is an open system, in that the air used to apply the brakes is 

lost, and the air supply must be replenished before the brakes can operate. Repeated brake 

applications in succession (pumping the brakes) may prevent an air brake system from resupplying the air expended during braking quickly enough to maintain a supply of air 

sufficient to stop the vehicle.

Another distinct characteristic of an air brake system is the mechanical lag time, 

that is, the interval between the depression of the brake pedal and the application of the 

brakes. The lag time varies from about 0.20 to 0.55 second and may be longer in poorly 

maintained systems.41 The mechanical lag time adds to the overall stopping distance. For 

instance, at 50 mph, a vehicle travels at 73.30 feet per second. In a typical air brake system 

41 Timing limitations are identified in 49 CFR 571.121, the course materials of the Institute of Police 

Technology and Management’s Commercial Vehicle Inspection and Reconstruction course, and field testing 

conducted by Safety Board investigators from 1989 through 1998.
Factual Information 23 Highway Accident Report

for which the lag time is 0.50 second, the vehicle will travel an additional 36 feet from the 

moment of brake pedal depression until the brakes are fully applied.

Vehicles that are typically equipped with air brakes include dump trucks, large 

transport trucks, and many types of buses. Some motor homes also have air brakes. Air 

brakes are optional on many trucks in the 19,501- to 33,000-pound weight classes. 

According to an article in Heavy Duty Trucking,

42 an air brake system’s foundation brakes 

(drums and shoes) are large and can absorb a lot of heat. Hydraulic brakes typically wear 

out faster. In addition, air brake replacement parts are generally cheaper and more readily 

available than hydraulic brake system parts.

Automatic Slack Adjusters

ASAs, which are components of air brakes and are also known as automatic brake 

adjusters, have been offered as optional equipment on some commercial vehicles since the 

late 1960s. In 1992, the Safety Board noted, “The majority of truck tractors and about half 

the trailers currently being manufactured are equipped with automatic adjusters.”43 When 

the rule requiring automatic adjusters on all air brake-equipped vehicles built on or after 

October 20, 1994, was enacted,44 most heavy vehicles were already in compliance. The 

primary purpose of ASAs is to maintain brake adjustment levels without a mechanic or 

driver having to adjust the brakes manually. (See figure 10.)

ASA Manufacturers’ Guidance on Manually Adjusting ASAs. The Safety 

Board is aware of at least six companies that market ASAs.45 The service manuals of all 

the ASA manufacturers reviewed suggest, implicitly or explicitly, that ASAs should not 

have to be manually adjusted, except at the time of initial installation or when brake 

components are replaced. Further, the manuals suggest that if an ASA is out of 

adjustment, it means that a problem exists with the installation, the slack adjuster itself, or 

other foundation brake components. None of the service literature reviewed suggests that 

routine manual adjustment of ASAs is a proper course of action for brakes found to be out 

of adjustment (excessive pushrod stroke).

42 “Getting the Right Truck,” Heavy Duty Trucking, October 7, 2004. See 

<http://www.heavydutytrucking.com/200205/034a0205.asp>.

43 National Transportation Safety Board, Heavy Vehicle Airbrake Performance, Safety Study 

NTSB/SS-92/01 (Washington, DC: NTSB, 1992) 48.

44 Title 49 CFR 393.53(b).

45 The six are Haldex Brake Products Corporation, headquartered in Kansas City, Missouri; Bendix 

Commercial Vehicle Systems LLC, headquartered in Elyria, Ohio; Bendix Spicer Foundation Brake LLC, 

headquartered in Elyria, Ohio; Gunite Corporation, headquartered in Rockford, Illinois; Rockwell 

Automotive, which in 1997 became Meritor Automotive, of ArvinMeritor, Inc., headquartered in Troy, 

Michigan; and Crewson Industries, Inc., headquartered in Buffalo, New York. (Note: Although Bendix 

Spicer markets an ASA, Haldex actually manufactures the Bendix Spicer adjuster.)
Figure 10. Schematic of a Gunite automatic slack adjuster. (Adapted from a figure that 

appears in the Gunite Corporation Automatic Slack Adjuster Service Manual, June 

1994 edition.)

Link

Grease Fitting

Hex Extension

Clevis

1/2-inch or 5/8-inch 

Clevis Pin 

Boot 1/4-inch Clevis Pin 

Factual Information 24 Highway Accident Report

The accident truck was equipped with Gunite ASAs. The Gunite service manual 

states (bold print in original), “An automatic slack adjuster should not have to be 

manually adjusted except for initial installation and at the time of brake reline.”46

This manual also explains how to troubleshoot to find the cause of excessive pushrod 

stroke. It does not suggest that manual adjustment is a way to correct excessive pushrod 

stroke.

Further, according to ASA manufacturers, the adjuster will not hold adjustment as 

well when adjusted manually. Gunite, Haldex, and Bendix indicated to Safety Board 

investigators that they have not done any testing to show the relationship between manual 

adjustment of an ASA and the time (or number of brake applications) it may take for the 

adjuster to go back out of adjustment. The Haldex service manual states “Automatic 

adjusters should not be operated as manual adjusters except as may be necessary to get the 

vehicle off the road for service.”47 In the same publication, under questions and answers, 

the following question appears: “If automatic adjustment stops, can I operate it as a 

manual brake adjuster?” The answer provided in the manual is: “No. Completely check 

46 Gunite Corporation, Automatic Slack Adjuster Service Manual, publication ASA-100-1, dated June 

1994.

47 Haldex Service Manual for Automatic Brake Adjusters, publication L30033HBS, dated 

November 11, 2001.
Factual Information 25 Highway Accident Report

out foundation brake and adjuster to determine the cause of the problem. Repair or replace 

as needed to restore automatic adjustment.”

According to the ASA manufacturers, one of the reasons that ASAs should not be 

manually adjusted is that every time the adjusting nut is turned in a counterclockwise 

direction, the internal components experience additional wear. For the majority of ASAs, 

regular manual adjustment will cause premature wearing of the internal clutch, potentially 

reducing the effectiveness of the internal clutch operation, which is necessary for the 

automatic adjustment feature to work properly.48

Other Industry Views on Manual Adjustment of ASAs. Through the Truck 

Manufacturers Association, Safety Board investigators queried medium-heavy truck 

manufacturers to determine what information, if any, they provide about the manual 

adjustment of ASAs. Only Freightliner49 responded to the inquiry. Freightliner indicated 

that its manuals do not currently address manual adjustment of ASAs but stated that when 

it next updates its driver, maintenance, and service manuals, it will revise them to include 

warnings about manually adjusting ASAs.

Over the past 2 years, Safety Board investigators have asked truck mechanics, on a 

random basis, whether they manually adjust ASAs. The majority indicated that they 

manually adjust ASAs when they are out of adjustment.

Brake Information in State Driver’s Manuals

Every State produces a basic driver’s handbook or manual on obtaining a driver’s 

license. Each State is required to produce a CDL manual to provide information, specific 

knowledge, and details about testing procedures.50 The State manuals are based on models 

developed by the American Association of Motor Vehicle Administrators (AAMVA).51

The truck driver in the Glen Rock accident had a Maryland driver’s license (not a 

CDL). The Maryland Driver’s Handbook provides general information about the rules of 

the road and the operation of passenger cars. The handbook does not address driving on 

hills or mountains. It does address the topic of brake failure in “Special Driving Situations,” 

subsection “Emergencies.”52 The action suggested in case of brake failure is pumping the 

48 Manual adjustment will cause additional wear on the internal clutch on most ASAs because the 

adjusting hex has to be rotated counterclockwise. Rockwell (now ArvinMeritor) has a special pawl that can 

be removed in older adjusters or pulled in new models, which will release the clutch and no damage will 

occur. Crewson Industries has recently introduced a new adjuster with a “push pin” release that also releases 

the clutch.

49 Headquartered in Portland, Oregon, Freightliner Group is a leading North American truck and 

specialty vehicle manufacturer.

50 Title 49 CFR 383.131.

51 Founded in 1933, the AAMVA is a voluntary, tax-exempt, nonprofit, educational organization that 

develops model programs affecting motor vehicle administration, police traffic services, and highway safety 

and provides information concerning these disciplines. It also represents the U.S. and Canadian State and 

Provincial officials who administer and enforce motor vehicle laws.

52 Maryland Driver’s Handbook, 48.
Factual Information 26 Highway Accident Report

brakes. (Cars are equipped with hydraulic brake systems. For a hydraulic braking system, 

pumping the brakes may compress air in the line or free a restricted braking component. If 

a hydraulic system is breached, pumping the brakes may provide some braking until there 

is a complete loss of fluid.) No sections in this handbook address air brakes.

The Maryland CDL Manual53 addresses mountain driving, providing information 

about using lower gears to descend a hill and maintaining a maximum safe speed that will 

not exceed the vehicle braking limits. The manual states, “When you reach your maximum 

safe speed apply your brakes sufficiently enough to decrease your speed by 5 mph.” It also 

cautions about brake fade and the need for frequent brake adjustment checks.

In its section on air brakes, the Maryland CDL Manual describes the air brake 

system and how it works. It has specific information on low air pressure warnings and air 

reservoir gauges, inspection of an air brake system to ensure that it is functioning and 

adjusted properly, and brake lag time and the additional travel distance it entails until 

effective braking takes place. The manual indicates that a brake lag time of 0.50 second or 

more is possible.

The Maryland CDL Manual contains “Test Your Knowledge” features following 

its information sections. The “Test Your Knowledge” segment for the air brake section 

addresses (1) low pressure warning lights, (2) using brakes on downgrades, (3) the causes 

of brake failure, and (4) reducing gear before descending a hill.

Submission to the AAMVA for the Model Commercial Driver License Manual

The AAMVA publishes a model Commercial Driver License Manual that all 50 

States use; few, if any, States make specific changes for their State manuals. The manual 

was last published 10 years ago.54 In August 2004, a coalition of five ASA manufacturers55

endorsed inclusion of the following language regarding ASAs in the new model

Commercial Driver License Manual, which was distributed on January 3, 2006.

All airbrake vehicles manufactured since October 20, 1994 are required to have 

automatic brake adjusters, also known as ASAs.

Automatic adjusters should not have to be manually adjusted except when 

performing maintenance on the brakes and during the installation of the brake 

adjusters. In a vehicle equipped with automatic adjusters, when the pushrod stroke 

exceeds the legal brake adjustment limit, it is an indication that a mechanical 

problem exists in the adjuster itself, a problem with the related foundation brake 

components, or that the adjuster was improperly installed.

53 Maryland Department of Transportation, Motor Vehicle Administration, Maryland CDL Manual

(Glen Burnie, MD: Maryland Department of Transportation, April 1994).

54 Commercial Driver License Manual, Version 2.0. (AAMVA, 1996).

55 The five manufacturers are ArvinMeritor, Bendix, Crewson, Gunite, and Haldex. Although Bendix 

Spicer markets an ASA, the adjuster is manufactured by Haldex. Bendix Spicer deferred to Haldex to 

comment on the proposed wording of the new text to be included in the manual.
Factual Information 27 Highway Accident Report

The manual adjustment of an automatic adjuster to bring a brake pushrod stroke 

within legal limits is generally masking a mechanical problem and is not fixing it. 

Further, routine adjustment of most automatic adjusters will likely result in 

premature wear of the adjuster itself. It is recommended that when brakes 

equipped with automatic adjusters are found to be out of adjustment, that the 

driver take the vehicle to a repair facility ASAP to have the problem corrected.

The manual adjustment of an automatic adjuster should only be used as a 

temporary measure to correct the adjustment in an emergency situation, as it is 

likely the brake will soon be back out of adjustment since this procedure usually 

DOES NOT fix the underlying adjustment problem.

(Note: Automatic brake adjusters are made by different manufacturers and do not 

all operate the same. Therefore, the manufacturer’s Service Manual for the 

specific automatic adjuster being used should be consulted prior to 

troubleshooting a brake adjustment problem.)

According to the AAMVA, this language is included in the new model

Commercial Driver License Manual.

Commercial Vehicle Inspection Programs

Both the FMCSA and some States require commercial vehicle inspections. The 

FMCSA requires every commercial vehicle (engaged in interstate commerce) to undergo an 

annual inspection.56 This Federal requirement can be fulfilled in three different ways. The 

first method is by a State inspection. The District of Columbia and 21 States, including 

Pennsylvania, require commercial vehicles (engaged in intrastate or interstate operations) to 

undergo annual vehicle inspections; 3 States57 have voluntary commercial vehicle inspection 

programs. In these 25 jurisdictions that have a qualifying inspection program, the Federal 

requirement can be met by a State inspection.58 To implement its inspection program, the 

State either operates its own inspection stations or, as in Pennsylvania, the State authorizes 

privately owned and operated garages and repair facilities to conduct the inspections.

The second method by which the Federal inspection requirement can be met 

applies in those States without a qualifying State inspection program. In such States, a 

motor carrier can either conduct the inspection itself or have it conducted at a repair 

facility. In either case, to meet the Federal requirement, the individuals performing the 

inspection must be qualified under 49 CFR 396.19.

56 See 49 CFR 396.17 and the FMCSRs, appendix G to subchapter B, Minimum Periodic Inspection 

Standards.

57 Arkansas, Illinois, and Oklahoma.

58 A State inspection will fulfill the Federal inspection requirement if the vehicle is inspected under a 

mandatory State inspection program in Alabama, California, Connecticut, Hawaii, Louisiana, Maine, 

Maryland, Michigan, Minnesota, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode 

Island, Texas, Utah, Vermont, Virginia, West Virginia, Wisconsin, or the District of Columbia. (Of these, 

Alabama, California, Connecticut, Michigan, Minnesota, New Jersey, New York, Ohio, and Wisconsin have 

inspection programs that do not cover all commercial motor vehicles.) In the three States with voluntary 

State inspection programs—Arkansas, Illinois, and Oklahoma—the voluntary State inspection will also 

satisfy the Federal inspection requirement.
Factual Information 28 Highway Accident Report

The third way the Federal annual inspection requirement can be fulfilled is through 

a State or other jurisdiction’s roadside inspection,59 as long as it meets the minimum 

requirements found at 49 CFR 396.17. The CVSA North American Standard Inspection 

procedures developed by the CVSA and the FMCSA fulfill these minimum requirements, 

and the CVSA procedures are to be used by all roadside inspectors. The Safety Board 

reviewed the North American Standard Inspection training materials developed and 

maintained by the CVSA and the FMCSA’s National Training Center and found that they 

do not address the subject of manual adjustment of ASAs.

Inspector and Mechanic Certification Requirements

The ASAs on the accident truck were manually adjusted at different times by at 

least two individuals—a former Blossom Valley driver, who was a truck mechanic with 20 

years’ experience, and the mechanic from the Beasley Ford dealership in York, 

Pennsylvania. Both individuals were Pennsylvania State-certified truck inspection 

mechanics; the Ford dealership mechanic was also ASE certified.

Pennsylvania State-Certified Truck Inspection Mechanics. Two classes of 

inspectors perform annual vehicle inspections in Pennsylvania under PennDOT direction. 

Class 1 inspectors inspect cars and trucks under 17,000 pounds and class 3 inspectors 

inspect trucks and buses over 17,000 pounds and trailers over 10,000 pounds. Community 

colleges and private driving schools provide inspector training. According to Pennsylvania 

Code Section 175.28 “Certified inspection mechanics. (d) Certification requirements,”

A mechanic desiring to become certified: shall (1) be 18 years of age or older, (2) 

have a valid driver’s license for each class of vehicle which the mechanic will 

inspect, (3) have attended an approved 9-hour certification course and 

successfully completed the required written examination, (4) pass the required 

tactile test administered by a certified/qualified automotive instructor at an 

approved education facility. Recertification requires a mechanic to pass the 

required written examination every 3 years.

According to PennDOT, the instruction necessary to become a class 3 truck 

inspector requires an additional 3 or 4 hours, includes a practical test, and gives special 

attention to air brake systems. PennDOT officials told Safety Board investigators that 

inspectors are taught to recognize whether something is broken or not functioning, but 

they are not taught how to diagnose brake component problems.

The ASE. The ASE is an independent, nonprofit organization established in 1972 

to improve the quality of vehicle repair and service through the testing and certification of 

repair and service professionals. According to the ASE, about 420,000 professionals hold 

current certifications and work in every segment of the automotive service industry, 

including car and truck dealerships, independent garages, fleets, service stations, and 

franchises. Certification requirements include passing 1 of the ASE’s 40 exams and 

proving relevant work experience. To remain certified, those with ASE credentials must 

be retested every 5 years.

59 Title 49 CFR 396.23.
Factual Information 29 Highway Accident Report

The ASE medium-heavy truck test catalog contains eight tests, including test “T4-

Brakes.” A review of the test specifications and task list indicates that air brake diagnosis 

and repair make up 56 percent of the ASE brake test. Section 2 of this test, 

“Mechanical/Foundation,” includes item 3, termed “Inspect, adjust, repair, or replace 

manual and automatic slack adjusters.” The sample test questions do not address the 

manual adjustment of ASAs.

The ASE does not publish or endorse study guides for its tests, but several 

automotive repair guide companies do publish ASE study guides. One company’s ASE 

T4-Brake test study guide states, “Automatic slack adjusters may require periodic 

adjustment. The method varies by manufacturer.” Safety Board investigators reviewed all 

available ASA manufacturers’ service manuals; none suggest that ASAs may require 

periodic adjustment.

American Trucking Associations Technology and Maintenance Council

The American Trucking Associations, Inc., (ATA) Technology and Maintenance 

Council publishes recommended truck maintenance practices. Its Recommended Practice 

609B (RP 609B) document, Manual and Automatic Slack Adjuster Removal, Installation 

and Maintenance, provides information regarding the removal, installation, operation, 

maintenance, and selection of heavy-duty vehicle manual slack adjusters and ASAs. The 

following statements appear in this document:

{CAUTION} Self-adjusting brake adjusters do not eliminate or reduce the need 

for periodic inspection and maintenance of the adjuster components and attaching 

hardware.

However, manual adjustment can be made temporarily to get a vehicle to a 

maintenance facility for inspections and repair, if necessary.

A self-adjusting brake adjuster should not have to be manually adjusted except for 

installation and at brake reline.

RP 609B also provides a preventative maintenance schedule for both manual slack 

adjusters and ASAs.

Owner-Operator Independent Driver Association Survey

In 2000, the Owner-Operator Independent Drivers Association (OOIDA) conducted 

a 13-question driver survey of its membership and found that 65 percent of owner-operator 

drivers and 59 percent of company drivers had ASAs on their equipment.60 When asked, 

“What brake maintenance do you personally perform?,” 75 percent of the owner-operators 

and 57 percent of the company drivers indicated that they adjust their brakes. Almost 

20 percent of all responding drivers indicated that ASAs are the biggest problem with 

current brake systems. Drivers said ASAs are unreliable, excessively depended upon, 

maintained improperly, and more difficult to adjust than manual slack adjusters are.

60 Rick Craig, “The Driver Perspective,” Report of Proceedings of the North American Brake Safety 

Conference, September 15-16, 2000 (Toronto, Canada: CVSA, 2001) 57.
Factual Information 30 Highway Accident Report

Operation Air Brake

The CVSA and the Canadian Council of Motor Transport Administrators 

(CCMTA)61 sponsor the Operation Air Brake campaign, which consists of 2 days of 

brake inspections (1 day of announced and 1 day of unannounced inspections) 

conducted annually by CVSA member agencies. Since 1998, the CVSA has gathered 

statistics from Operation Air Brake that show that inspected brakes equipped with ASAs 

are placed out of service between 3.5 and 4.2 percent of the time, and inspected brakes 

equipped with manual slack adjusters are placed out of service between 8.3 and 9.1 percent 

of the time.

The 2003 Operation Air Brake campaign included a driver survey on air brake 

adjustment knowledge. The survey, conducted during the brake check days and other 

enforcement activities, included 11 questions, and 4,055 professional drivers 

responded. According to preliminary results,62 “The responses reveal an overwhelming 

level of misunderstanding about the importance of brake adjustment and correct 

methods to inspect the adjustment on their vehicles.” About three-quarters of the 

drivers who responded indicated they were company drivers and the rest indicated they 

were owner-operators. The average experience level of both groups was 14.8 years of 

driving.

The survey asked the drivers what source they rely on the most for providing 

reliable information about air brakes. The sources identified by the drivers were 

classroom training (28 percent); their company (30 percent); books, manuals, and 

videos (32 percent); and other drivers (10 percent). The Operation Air Brake Committee 

indicated that the drivers who identified books, manuals, and videos as their source of 

information regarding air brakes seemed to have a better understanding of the proper 

operation of air brakes than the other drivers and had fewer brake out-of-service 

violations.

In addition, the survey asked drivers a question about their beliefs concerning 

ASAs. Figure 11 shows the results.

In 2004, the CVSA, recognizing the importance of air brake education and 

proper brake adjustment, included a special education component in Operation Air 

Brake. On September 5, 2004, CVSA inspectors conducted demonstrations and 

provided educational materials to drivers and mechanics about achieving proper brake 

operation, recognizing potential brake problems, and understanding the need for 

properly maintained brakes. Some of the educational efforts took place at the 10 

TravelCenters of America truck stops in Ohio; the Husky Truck Stop near Regina, 

Saskatchewan; and the TravelCenters of America truck stop near Baltimore, Maryland. 

61 The CCMTA is the official organization in Canada for coordinating all matters dealing with the 

administration, regulation, and control of motor vehicle transportation and highway safety. The CCMTA 

includes members from all Canadian governments (Provincial, Territorial, and Federal), as well as associate 

members from transportation-related organizations. See <http:www.ccmta.ca>.

62 From Operation Air Brake campaign—Report of Driver Survey on Air Brake Adjustment Knowledge 

2003, draft.
Factual Information 31 Highway Accident Report

According to the CVSA,63 brake-related defects continue to be the most significant and 

frequent violations that safety inspectors discover during roadside inspections.

Figure 11. Responses to 2003 Operation Air Brake driver survey question about 

automatic slack adjusters. (Source: Commercial Vehicle Safety Alliance)

Beliefs About Automatic Brake Adjusters 

140

2179

1373

362

n/a never go out of

adjustment

can be adjusted

by drivers with

the proper tools

need adjustment

on a regular

basis

The CVSA also developed a pamphlet on air brake adjustment for distribution 

during the 2004 Operation Air Brake campaign. (See appendix C for a photocopy of the 

pamphlet, entitled Air Brake Adjustment—Why is it so important?) The CVSA told Safety 

Board staff that it has printed 35,000 copies of the pamphlet, and demand for the pamphlet 

has been strong. The pamphlet includes the following language:

READJUSTING AUTOMATIC BRAKE ADJUSTERS

Automatic brake adjusters normally don’t require manual readjustment. If you 

have a brake that is over-stroking and it has an automatic brake adjuster, you have 

a problem with the brake or the adjuster. If you readjust it, you aren’t really fixing 

the problem. The same is true if someone else only readjusts it, the problem is still 

there.

A manual readjust may bring the brake back into compliance and improve the way 

the brake operates, but it will only be temporary.

Table 7 shows the results of the 2005 Operation Air Brake unannounced brake 

inspections, indicating the out-of-service rates in the United States and Canada and the 

percentage of manual and automatic slack adjuster-equipped brakes found out of 

adjustment.

63 See additional information at <http://www.cvsa.org/programs/04operation_airbrake.html> and 

<http://www.cvsa.org/latestnews/cvsa_latestnews.html>.
Factual Information 32 Highway Accident Report

Table 7. Summary of May 5, 2005, CVSA Operation Air Brake results (unannounced 

inspections).

The Operation Air Brake Committee determined that, based on the success of the

2004 Operation Air Brake education event, a major education and awareness campaign

directed at drivers and mechanics would help address the chronic problems associated

with air brake compliance, inspection, and maintenance. In 2005, the committee dedicated

August 28 through September 3 as Brake Safety Awareness week. This event replaced the

Operation Air Brake annual announced brake check day for 2005. The committee asked

that each jurisdiction conduct one or more educational or awareness events during Brake

Safety Awareness week.

Commercial Vehicle Statistics

Preliminary data from the FMCSA’s study on large truck crash causation64

indicate that in multivehicle crashes in which the truck was at fault, 38 percent involved

vehicle equipment problems. Earlier data from Michigan65 suggest that truck brake

conditions may have a role in crashes in which trucks strike other vehicles. In rear-end

crashes in which the truck was the striking vehicle, the incidence of defective or poorly

adjusted truck brakes was almost twice as high as in cases in which other vehicles struck

trucks. A 2003 General Accounting Office analysis66 of NHTSA crash data for all vehicles

during the period 1997 to 2001 found about 778,000 crashes in which police identified a

Location

Number 

of trucks 

checked

Percent out of 

service for 

brake 

adjustment

Percent out of 

service for 

brake 

components

Percent out 

of service 

for brakes

Percent of 

brakes out of 

adjustment

Manual Auto

Canadian 

jurisdictions 

(10 Provinces)

2,857 6.3 6.1 12.1 7.1 2.8

U.S. 

jurisdictions 

(27 States)

14,479 12.0 8.8 18.4 8.9 4.6

Total 17,336 11.1 8.4 17.4 8.7 4.2

64 Briefing by Ralph Craft of the FMCSA during Session 119 of the Transportation Research Board’s

annual meeting, held on January 9, 2005, in Washington, D.C.

65 The Fatal Accident Complaint Team, Michigan State Police Motor Carrier Enforcement Division,

project involved investigating fatal commercial vehicle crashes in Michigan from 1996 to 2001 to determine

why the crashes occurred. Each truck was subjected to a North American Standard Inspection (CVSA level 1),

evaluating its precrash compliance with motor vehicle and driver regulations. Ralph Craft, FMCSA Analysis

Brief, Rear-End Crashes Involving Large Trucks, FMCSA-RI-03-019.

66 U.S. General Accounting Office, Highway Safety: Research Continues on a Variety of Factors that

Contribute to Motor Vehicle Crashes, GAO-03-436 (Washington, DC: GAO, March 2003). (Note: The

General Accounting Office has since changed its name to the Government Accountability Office.)
Factual Information 33 Highway Accident Report

specific vehicle feature that might have contributed to the crash. Of those 778,000 crashes,

brake systems were identified as a contributing factor 29 percent of the time.

In addition, an examination67 of NHTSA’s 1998 National Automotive Sampling

System/General Estimate System data shows that, in crashes involving a commercial

vehicle, when vehicle defect was a likely factor, an estimated 36 percent of the crashes

involved the braking system. These same data indicate that crashes involving the brake

system as a contributing factor accounted for 49 percent of the injuries associated with

commercial vehicle crashes.

The Glen Rock accident involved a straight truck. UMTRI data68 for the year 2000

indicate that straight truck power configurations accounted for 33.3 percent of the 5,275

trucks involved in fatal accidents. In addition, 433 of these straight trucks (24.7 percent)

were dump trucks. The drivers of 34.2 percent of the straight trucks and 32.9 percent of

the straight trucks with trailers did not have CDLs.

The Safety Board canvassed the heavy truck manufacturers through the Truck

Manufacturers Association to determine how many trucks weighing less than 26,000

pounds are equipped with air brakes. Only International and Freightliner responded.

International indicated that in 2004 it sold about 15,000 class 6 (19,501- to 26,000-pound)

vehicles, about 40 percent of which were equipped with air brakes. Table 8 shows the

information provided by Freightliner.

Table 8. Domestic Freightliner vehicles built in the past 2 years.

In the past 2 years, Freightliner has built 14,231 vehicles that weigh less than

26,000 pounds, and 84 percent of these vehicles had air brakes. The 1997 U.S. vehicle

inventory and use survey69 indicated that 729,300 vehicles in the light-heavy or class 6

category (19,501 to 26,000 pounds) were in use. The recent Freightliner and International

data show that many of these vehicles have air brakes. The latest U.S. vehicle inventory

67 U.S. Department of Transportation, Federal Motor Carrier Safety Administration, On-Board Sensors

for Determining Brake System Performance, Task Order 3 of the Commercial Motor Vehicle Technology

Diagnostics and Performance Enhancement Program, FMCSA-PSV-04-001 (Washington, DC: USDOT,

December 2003).

68 Anne Matteson and Dan Blower, Trucks Involved in Fatal Accidents Factbook 2000, Center for

National Truck Statistics, University of Michigan Transportation Research Institute, UMTRI 2003-20 (Ann

Arbor, MI: July 2003).

Class (weight in pounds) Air brakes Hydraulic brakes Total % air brakes

Class 4 (14,001–16,000) 0 7 7 0 

Class 5 (16,001–19,500) 32 696 728 4

Class 6 (19,501–26,000) 10,852 2,644 13,496 80 

Class 7 (26,001–33,000) 16,685 356 17,041 98 

Class 8 (33,001 and up) 97,360 0 97,360 100

69 This regularly conducted survey provides information on the physical and operational characteristics

of the Nation’s truck population. See U.S. Department of Commerce, U.S. Census Bureau, 1997 Economic

Census, Vehicle Inventory and Use Survey, EC97TV-US, issued October 1999.
Factual Information 34 Highway Accident Report

and use survey, conducted in 2002,70 included a question about brakes. Evaluation of the 

survey’s raw data showed that 516,110 (30 percent) of the 1,709,574 vehicles in the 

19,501- to 26,000-pound weight class were equipped with air brakes.

El Cerrito, California, Accident

Since the Glen Rock accident, the Safety Board has investigated another accident 

involving loss of braking capability on a steep incline, out-of-adjustment brakes, and ASAs. 

About 1:26 p.m., Pacific daylight time, on August 26, 2003, a 3-axle Kenworth dump truck, 

in combination with a 2-axle transfer-bin semitrailer,71 had been hauling hot asphalt to a 

construction site on top of a mountainous hillside in El Cerrito, California. The truck driver 

drove the truck to the top of Moeser Lane, unhooked the transfer-bin semitrailer, and started 

down Moeser Lane to a construction site 3 or 4 blocks from the top of the hill. The 

downgrade on the hill varied between 15 and 20 percent. According to the truck driver, he 

attempted to downshift to a lower gear and thought he had the truck in gear, but the sound of 

the engine indicated that the truck was stuck in neutral. The truck started to speed up, and the 

driver was unable to bring it under control using the service brakes. He recalled that he was 

getting some braking, but it did not slow the truck enough to bring it under control. The truck 

continued down the hill, while the driver sounded the truck’s horn. The truck struck six 

vehicles, injuring some of the occupants. About a mile down the hill, the truck ran off the 

right side of the roadway at the corner of Moeser Lane and Richmond Street and struck a 

utility pole, a gas line, and a house before coming to rest on its left side near the house.

During the collisions and rollover, most of the hot asphalt from the bed of the truck 

was scattered, and some of it landed in the adjacent street and neighboring yards. The gas 

line the truck had struck ruptured and ignited. The fire destroyed the house that had been 

struck and the front of the accident truck; it also damaged gas and electric utility systems, 

resulting in a local power outage to about 20,000 homes. As a result of this accident, seven 

people were injured.

Truck Information. The accident truck was a 1991 Kenworth model T-600A, 3-

axle dump truck, with a sleeper cab. (The truck was originally manufactured as a 3-axle 

truck tractor, but it had been converted to a dump truck.) It was equipped with a Detroit 

Diesel Series 60 engine with a Jacobs Engine Brake, an Eaton-Fuller RTX14609BP 9-

speed transmission, a Ross TAS65 power steering gearbox, and a rear axle with a 3.90 

ratio. The factory-listed GVWR for the truck was 50,000 pounds. The truck was equipped 

with a standard air brake system with S-cam brakes. It did not have an ABS. Only the 

second axle (first drive axle) was equipped with spring parking/emergency brakes. The 

truck was equipped with Gunite ASAs.

70 The U.S. Census Bureau conducts a Vehicle Inventory and Use Survey every 5 years, during years 

ending in “2” and “7.” The Safety Board analyzed the raw data from the 2002 Economic Census, Vehicle 

Inventory and Use Survey, using the GVWR information from the Vehicle Identification Numbers. (See 

<http://www.census.gov/suds/www/vius/2002.html>.)

71 The transfer bin in this case was a 2-axle dump semitrailer that requires the load from the powered 

dump truck to be dumped first. Subsequently, by utilizing a ramp and cables, the bin body of the semitrailer 

is pulled onto the dump truck and dumped in the normal fashion, by raising the truck bed.
Factual Information 35 Highway Accident Report

Brake Inspection and Testing. The California Highway Patrol obtained the brake

pushrod measurements summarized in table 9 on scene. No further measurements were

possible due to the slack adjusters being “backed off” so that the brake drums could be

removed for inspection.

Table 9. El Cerrito Kenworth truck brake test summary.

All six wheels on the truck were equipped with Gunite ASAs. Safety Board

investigators and Gunite representatives examined and tested the slack adjusters and

found that the adjustment clutch was worn out for four of the six adjusters (left front, left

rear, second left rear, and second right rear). Examination of the date codes and serial

numbers revealed that five of the six adjusters were original equipment and had been on

the truck since it was manufactured in 1991. The adjuster on the right rear, which was in

adjustment, was the only one that had been replaced since the truck was new.

Driver Information. The 24-year-old truck driver was the owner of the accident

truck. He held a valid CDL with a March 26, 2006, expiration date, and a valid medical

certificate with an April 25, 2005, expiration date. He had graduated from the A. B. Truck

Driving School in San Jose, California, on August 23, 2001.

The driver stated that on the morning of the accident, he had [manually] adjusted

the brakes on the tractor and transfer-bin dump trailer. He said he had used a 9/16-inch

wrench on the trailer72 and a smaller one for the dump truck brakes.73 In addition, the

driver stated that his father was also a truck driver and had told him that bad brakes could

Axle

Air chamber 

size

Slack arm 

lengthA

Pushrod 

stroke

Adjustment 

limitB Rated strokeC

Left front T-16 5 1/2 in. Damaged 1 3/4 in. 2 1/4 in.

Right front T-16 5 1/2 in. 1 1/2 in.D 1 3/4 in. 2 1/4 in.

Left rear T-30 5 1/2 in. 2 1/2 in. 2 in. 2 1/2 in.

Right rear T-30 5 1/2 in. 1 7/8 in. 2 in. 2 1/2 in.

2nd left rear T-30 5 1/2 in. 2 5/8 in.E 2 in. 2 1/2 in.

2nd right rear T-30 5 1/2 in. 2 3/8 in. 2 in. 2 1/2 in.

A

The distance between the center of the splined camshaft and the center of the clevis pin, which secures the pushrod to

the slack adjuster; also known as the “lever arm length.” B

The maximum pushrod stroke permitted. The values used for the “brake adjustment limit” are those in the CVSA North

American Standard Out-of-Service Criteria. (Revised edition, April 2003.) CThe total length the pushrod can travel inside the air chamber. (When the “pushrod stroke” is equivalent to the “rated

stroke,” generally no braking forces are obtained when the brakes are applied.) DDue to fire damage, this brake was measured using a steel bar to pry back the slack adjuster arm and, as measured in

this manner, it was in legal adjustment. However, due to inherent variables, including the length and positioning of the

bar and the amount of force exerted by the inspector, the measurement method lacked the consistency obtained when

making a measurement pneumatically. A slightly higher pushrod stroke is usually obtained by using 80 to 100 psi of

air.

EThis brake was completely “bottomed out” during a static cool stroke, indicating that it was not providing any braking

force, even without being heated or overheated.

72 The transfer bin semitrailer had manual slack adjusters and required the use of a 9/16-inch wrench to

adjust them. A 9/16-inch wrench is the normal adjusting tool for manual slack adjusters.

73 According to Gunite’s Automatic Slack Adjuster Service Manual, ASA 100-1 (June 1994), a 7/16-

inch wrench is used for the hex-adjusting nut.
Factual Information 36 Highway Accident Report

mean his life. The driver said that he [manually] adjusted the brakes twice a week. The

driver also said that he did not know he was not supposed to [manually] adjust an ASA.

Other Investigations

In four additional recent accident investigations, the Safety Board has encountered

different brake maintenance problems involving ASAs found out of adjustment or not

functioning. These accidents involved ASAs produced by several different manufacturers.

Table 10 lists the investigations and the maintenance problems.

Table 10. Recent investigations involving ASA maintenance problems.

Accident investigation Automatic slack adjuster

Date Location Manufacturer Maintenance problem

May 31, 2001 Mountainburg, 

ArkansasA

Rockwell A broken spring brake and

incorrect installation of a brake

chamber

April 16, 2003 Hebron, KentuckyB Haldex and Bendix Worn clevis and clevis pins

March 12, 2004 Gardens Corner, 

South CarolinaC

Crewson Two adjusters on two different

school buses lacked grease

July 16, 2004 Chelsea, MichiganD Haldex Worn teeth on exterior control

arm

ANational Transportation Safety Board, Collision Between Truck-Tractor Semitrailer and School Bus Near 

Mountainburg, Arkansas, May 31, 2001, Highway Accident Report NTSB/HAR-02/03 (Washington, DC: NTSB, 2002). BPublic Docket HWY-03-M-H028.

CPublic Docket HWY-04-M-H018.

DPublic Docket HWY-04-M-H031.
37 Highway Accident Report

Analysis

The Glen Rock accident involved an untrained truck driver operating an 

overloaded, air brake-equipped vehicle with poorly maintained, out-of-adjustment brakes 

on a steep and weight-restricted hill, over which the truck was not permitted to travel. This 

analysis first discusses the factors and conditions the Safety Board was able to exclude as 

neither causing nor contributing to the accident. It then provides a brief overview of the 

accident events and a detailed discussion of the following major safety issues: (1) 

maintaining air brakes equipped with ASAs, (2) knowledge and skills needed to drive air 

brake-equipped vehicles, and (3) motor carrier oversight.

Exclusions

The accident occurred on a 3.4- to 13-percent grade on Church Street in the 

Borough of Glen Rock. Church Street had a load weight restriction, which was properly 

signed. The driver passed several load weight restriction signs before encountering the 

hill. First responders were on scene within 1 minute, and local fire departments and three 

ambulance services transported patients to area hospitals. Therefore, the Safety Board 

concludes that although the highway’s design included a steep grade, it was appropriately 

signed and, therefore, was not a factor in the accident; also, the emergency response was 

effective and appropriate.

Accident Discussion

The 1995 Ford dump truck was overloaded by 600 pounds (or about 2.3 percent of 

its GVWR of 26,000 pounds) and was proceeding southbound on Church Street, which 

has a steep downgrade. Safety Board-conducted computer simulations showed that the 

overloaded condition of the truck made a 5° F difference in brake temperature (final brake 

temperature of 456° F at 26,600 pounds and 451° F at 26,000 pounds) and did not 

noticeably affect the braking capability of the truck.

The driver stated that he was traveling 25 to 35 mph, that he stopped the truck at 

the top of the hill, that he did not select a lower gear, and that, as he started down the hill, 

he pumped his brakes but the truck would not slow and instead began to speed up. He also 

said that about a quarter of the way down the hill, he lost his brakes, and the brake light 

began to flash.74 He knew the flashing light meant he had brake problems, because his 

74 Postaccident testing showed that the red brake warning light would come on when the brake air 

pressure dropped below 70 psi, and the rear parking brakes would have been applied when the pressure 

dropped below 40 psi. However, because the rear brakes were so far out of adjustment, the parking brakes 

would have had little or no effect on slowing the truck.
Analysis 38 Highway Accident Report

boss and a coworker had told him that if the brake light flashed, he did not have enough 

[air brake] pressure. Unfortunately, as he later told investigators, he did not know that 

pumping the brakes depleted the air pressure. Postaccident examination of the truck 

brakes showed that both rear brakes were significantly out of adjustment (they exceeded 

the adjustment limit by 1/2 inch), which would have resulted in little or no brake force for 

the rear wheels, even with enough air. The front brakes were well within adjustment 

limits. However, without sufficient air pressure, the front brakes would also have been 

ineffective. Computer simulations confirmed that the rear brakes provided little or no 

braking force but that the truck might have been stopped with the front brakes if the driver 

had not depleted the air pressure by pumping the brakes.

Therefore, the Safety Board concludes that, based on the truck driver’s statements 

about pumping the brakes, postaccident examination of the brakes, and results from 

computer simulations, the accident truck did not have sufficient braking capability to stop 

before the initial impact with the stopped cars.

In the course of its investigation, the Safety Board considered whether the truck 

driver’s condition might have affected the outcome of the accident. According to the 

SRPD, the Glen Rock accident truck driver admitted previous use of cocaine, heroin, rock 

cocaine, hydrocodone, and marijuana. Postaccident toxicological tests found morphine,75

metabolites of cocaine,76 and a metabolite of marijuana77 in the truck driver’s urine. 

Postaccident testing results for alcohol were negative. The toxicological findings indicated 

that, in all likelihood, the driver had consumed cocaine and heroin78 in the 2 days 

preceding the accident, despite his statement that he had last used cocaine about 2 weeks 

before the accident. However, testing limitations (blood and urine were drawn 3 and 3 1/4 

hours, respectively, after the accident, and the sample sizes were insufficient to permit 

additional testing)79 preclude a determination as to whether the driver was under the 

influence of cocaine and morphine at the time of the accident. The effects of cocaine vary 

among individuals; the drug’s manifestations can include restlessness, increased risktaking, and excitement and/or aggression. Cocaine also interferes with sleep. Morphine is 

noted for causing drowsiness, nausea, and respiratory depression, in addition to its 

75 Morphine, a narcotic analgesic, is both a commonly used prescription pain reliever and the active 

ingredient in several common prescription medications and drugs of abuse. Morphine has a plasma half-life 

of about 2 to 3 hours. Following an oral dose, about 60 percent is excreted in the urine within 24 hours, and 

about 3 percent of the dose is excreted as free morphine within 48 hours. Morphine is initially eliminated 

from the blood fairly quickly. (Clarke’s Analysis of Drugs and Poisons, London: Pharmaceutical Press. 

Electronic version, 2004.)

76 Cocaine has a plasma half-life of 0.7 to 1.5 hours, depending on the dose. Elimination of cocaine and 

its metabolites from the urine is typically complete within 48 hours of ingestion. In plasma, it is usually 

eliminated within 18 to 24 hours. (See Clarke’s Analysis.)

77 Marijuana, a psychomimetic/mild hallucinogen, is a common drug of abuse. Its active ingredient, 

Δ9-THC, can be measured in plasma within seconds after inhalation. It has a plasma half-life of about 2 

hours among frequent users, or about 1.5 hours otherwise. Its active metabolite, 11-hydroxy-Δ9-THC, has a 

half-life of about 120 to 144 hours, depending on frequency of use, with the longer half-life typical of 

infrequent users. Δ9

-THC metabolites have been detected in urine for up to 12 days following a single oral 

dose. (See Clarke’s Analysis.)

78 Morphine is the primary active metabolite of heroin.

79 The driver’s blood was not tested for cocaine, cocaine metabolites, or morphine.
Analysis 39 Highway Accident Report

analgesic properties. The presence of THC metabolites in the driver’s urine but not the

plasma indicates the driver had consumed marijuana in the days (or weeks) preceding the

accident but was not under the influence of the drug at the time of the collision.

The Safety Board also considered the possibility that fatigue could have affected

the truck driver’s performance. Because the driver operated within a 100-mile radius of

the home terminal and returned to that location every day, he was not required to maintain

status-of-duty records. When requested by the Safety Board, Blossom Valley was unable

to provide the driver’s time records, despite being required by regulation to maintain such

records. Consequently, the driver’s work schedule could not be established. In addition,

the Safety Board could not adequately assess the impact of the driver’s drug use on his

sleep patterns.

The accident driver’s self-reported actions at the time of the accident suggest that

he was alert and oriented toward the immediate situation. The driver stated that as he

started down the hill, he pumped the brakes but could not stop the truck. In addition, he

said that when he saw children at the bottom of the hill, he leaned out of the window and

yelled, “No brakes, get out of the way.” Such actions do not indicate that his alertness was

impaired or that drugs or fatigue affected his response to the emergency. The 35-mph

impact speed, derived from the physical evidence, suggests that the truck driver attempted

to brake the truck as it sped down the hill. Had he been so impaired by drugs or fatigue

that he made no effort to brake the truck as it traveled down the hill, the speed of the truck

would have been greater. Given the out-of-adjustment rear brakes and the truck driver’s

lack of experience using air brakes, which resulted in his pumping the brakes, the truck

did not have sufficient braking capability to stop. Therefore, the Safety Board concludes

that although it cannot be determined if drugs or fatigue impaired the driver’s

performance, he most likely could not have stopped the truck before the accident

occurred.

Air Brakes

The rear air brakes of the accident truck were out of adjustment to the point that they

had little or no braking capability. The Safety Board has found poorly maintained air brakes

to be a causal factor in previous accident investigations80 and has been concerned about the

80 (a) National Transportation Safety Board, Francisco Flores Truck/Pickup Truck with Camper and

Trailer Collision, U.S. Route 395, Bishop, California, June 29, 1974, Highway Accident Report

NTSB/HAR-75/05 (Washington, DC: NTSB, 1975). (b) Texas Bus Lines, Inc., Charter Bus State Route 7,

Near Jasper, Arkansas, June 5, 1980, Highway Accident Report NTSB/HAR-81/01 (Washington, DC:

NTSB, 1981). (c) Direct Transit Lines, Inc., Tractor-Semitrailer/Multi-Vehicle Collision and Fire, U.S.

Route 40, Frostburg, Maryland, February 18, 1981, Highway Accident Report NTSB/HAR-81/03

(Washington, DC: NTSB, 1981). (d) Eureka Springs, Arkansas, September 13, 1985, Highway

Accident/Incident Summary Report NTSB/HAR-87/01/SUM (Washington, DC: NTSB, 1987). (e) Braking

Deficiencies on Heavy Trucks in 32 Selected Accidents, Safety Study NTSB/SS-88/06 (Washington, DC:

NTSB, 1988). (f) Collision Between Mission Consolidated Independent School District School Bus and

Valley Coca-Cola Bottling Company, Inc., Tractor-Semitrailer, Intersection of Bryan Road and Texas

Farm-To-Market Road 676, Alton, Texas, September 21, 1989, Highway Accident Report NTSB/HAR-90/02

(Washington, DC: NTSB, 1990). (g) Heavy Vehicle Airbrake Performance, Safety Study NTSB/SS-92/01
Analysis 40 Highway Accident Report

proper operation of air-braked vehicles for more than 30 years. As a result of previous 

investigations, the Board has made recommendations about disseminating information 

regarding on-road brake adjustment,81 distributing appropriate brake maintenance 

materials,82 equipping air-braked vehicles with visible adjustment indicators,83 making 

pretrip brake inspections,84 and establishing brake inspector qualifications.85 (Appendix D 

provides a history of previous Safety Board brake adjustment recommendations.)

Maintaining Air Brakes Equipped with Automatic Slack Adjusters

The majority of heavy trucks on the road are equipped with ASAs. All air-braked 

vehicles manufactured after 1994 are required to have them and, in 1992, the Safety Board 

found that about 65 percent of the vehicles inspected during the Heavy Vehicle Airbrake 

Performance safety study86 were already equipped with ASAs. These safety devices were 

introduced without a concentrated education effort being employed.

Problems Caused by Manually Adjusting ASAs. The postaccident inspection of 

the Glen Rock accident truck revealed that the two rear axle brakes were out of adjustment 

and produced little or no braking force. The front axle air chambers, which were slightly 

more than half the size of the rear chambers, were in proper adjustment. Yet, because the 

larger T-30 rear brakes produced little or no braking force, excessive strain was placed on 

the significantly smaller T-16 front brakes, which caused them to quickly overheat, 

resulting in severely diminished truck braking capability.

The truck was equipped with Gunite ASAs on all four brakes. After the accident, 

when the two rear adjusters were tested at the Gunite facility with the worn “quick-connect” 

clevises and clevis pins from the accident truck, the pushrod stroke would not go below 2 1/2 

inches, which is outside the adjustment limits, rendering the system incapable of producing 

braking force. However, when the ASAs were tested with new clevises and clevis pins, 

they functioned properly and the adjustment stayed well under 2 inches, which is within the

81 Safety Recommendation H-75-17. See appendix D for more information.

82 Safety Recommendations H-92-67, -72, and -74. See appendix D for more information.

83 Safety Recommendations H-92-50, -51, and -57. See appendix D for more information.

84 Safety Recommendation H-02-15. See appendix D for more information.

85 Safety Recommendations H-02-17 and -18. See appendix D for more information.

86 NTSB/SS-92/01.

(Washington, DC: NTSB, 1992). (h) Mayflower Contract Services, Inc., Tour Bus Plunge from Tramway 

Road and Overturn Crash, Palm Springs, California, July 31, 1991, Highway Accident Report NTSB/HAR93/01 (Washington, DC: NTSB, 1993). (i) Truck Loss of Braking Control on Steep Downgrade and Collision 

With a Vehicle Near Plymouth Meeting, Pennsylvania, April 25, 1996, Highway Accident Report 

NTSB/HAR-97/02 (Washington, DC: NTSB, 1997). (j) Motorcoach Loss of Control and Overturn, New 

Mexico State Route 475, March 2, 1999, Highway Accident Brief NTSB/HAB-01/01 (Washington, DC: 

NTSB, 2001). (k) Collision Between Truck-Tractor Semitrailer and School Bus Near Mountainburg, 

Arkansas, May 31, 2001, Highway Accident Report NTSB/HAR-02/03 (Washington, DC: NTSB, 2002). (l) 

Highway Accident Investigation HWY-02-MH-003 concerning an October 2001 work zone collision 

accident in Monaca, Pennsylvania. The Safety Board is also investigating an accident involving braking issues 

that took place in Sulphur Springs, Texas, in 2004.
Analysis 41 Highway Accident Report

adjustment limits and would provide adequate braking forces. Therefore, the Safety Board

concludes that at the time of the accident, the ASAs for all four of the accident truck’s brakes 

were capable of working properly; however, the quick-connect clevises and clevis pins for 

both rear brakes were worn to the extent that they prevented the ASAs from properly 

adjusting the brakes, thereby reducing the capability of the rear brakes.

The Safety Board reviewed the maintenance and inspection history of the accident 

truck, which had undergone four vehicle inspections between 2001 and the April 2003 

accident—three Pennsylvania State annual inspections (August 2001, March 2002, and 

January 2003) and one roadside inspection (April 2002). During two of these 

inspections—the 2002 roadside inspection and the 2003 State annual inspection—the rear 

brakes were found to be out of adjustment. After the 2002 roadside inspection, when the 

accident truck was placed out of service for out-of-adjustment brakes, the driver of the 

vehicle, who was also a truck mechanic, manually adjusted the ASAs. The Safety Board 

could find no record of further examination of the brakes by the company or the mechanic 

to discover why the brakes had been out of adjustment. During the 2003 State annual 

inspection, a Ford dealership mechanic found the rear brakes to be out of adjustment, and 

he manually adjusted the ASAs. In an interview with Safety Board investigators, he said 

he had adjusted the brakes and thought he had fixed the problem. Had he performed a 

more in-depth examination of the brake system, he probably would have found and 

replaced the worn clevises and clevis pins, which would have enabled the ASAs to adjust 

the brakes properly and might have prevented the accident.

The Gunite service manual gives specific instructions on how to conduct a torque 

test by turning the adjustment nut. If the Ford dealership mechanic had done a torque test, 

he might have realized that the adjuster itself was working properly. In addition, the Gunite 

service manual indicates that mechanics should “check the foundation brake for proper 

function; worn cam bushings, pins and rollers, broken springs, worn quick-connect clevis, 

worn clevis bushings and clevis pins. Repair as necessary and repeat the function test.”87

One reason that ASAs should not be manually adjusted is that every time the 

adjusting nut is turned in a counterclockwise direction, the internal components experience 

additional wear because the action abrades the internal adjusting mechanism. In the El 

Cerrito, California, accident, the driver stated that he manually adjusted the slack adjusters 

twice a week and had done so on the morning of the accident. Postaccident testing of the El 

Cerrito accident truck at the Gunite factory showed that three of the adjusting clutches were 

worn to the point that they could not hold an adjustment, probably due to their age and the 

deterioration caused by frequent manual adjustment. For the majority of ASAs, regular 

manual adjustment will cause premature wearing of the internal clutch, which is a 

necessary component for the automatic adjustment feature to work properly.88

87 Gunite Automatic Slack Adjuster Service Manual, ASA 100-1 (Gunite Corporation, June 1994) 7.

88 Manual adjustment will cause additional wear on the internal clutch on most ASAs, as the adjusting 

hex has to be rotated counterclockwise. Rockwell (now ArvinMeritor) has a special pawl that can be 

removed in older adjusters or pulled in new models, which will release the clutch so no damage will occur. 

Crewson Industries has recently introduced a new adjuster with a “push pin” release that also releases the 

clutch.
Analysis 42 Highway Accident Report

Various brake component problems can cause a pushrod stroke to go beyond the 

limits for producing adequate braking capability, causing the brakes to be out of service. 

These problems include, but are not limited to, worn cam bushings, worn or broken pins and 

rollers, broken springs, worn clevises (both quick-connect and standard), and worn clevis 

bushings and pins. When a driver or mechanic finds a pushrod stroke to be long and manually 

adjusts an ASA to correct the long stroke, he or she is masking the true problem with the 

brake, not fixing it. In all likelihood, the adjustment will be temporary. ASA manufacturers 

Gunite, Haldex, and Bendix indicated to Safety Board investigators that they do not know 

how long (how many brake applications) a manually adjusted ASA will hold an adjustment.

The drivers and mechanics who manually adjusted the ASAs on the trucks 

involved in the Glen Rock and El Cerrito accidents apparently did not understand that they 

were not fixing the underlying problem with the braking systems. They did not appreciate 

that when an ASA does not hold an adjustment, something is wrong with the adjuster itself 

or with some other foundation brake component. Therefore, the Safety Board concludes 

that the drivers and mechanics who manually adjusted the ASAs on the trucks involved in 

the Glen Rock and El Cerrito accidents did not look for underlying problems with the 

adjusters or related foundation brake components; consequently, they misdiagnosed the 

brake problems, probably because they were not properly educated on the function and 

care of ASAs and how they relate to foundation brake systems.

Manually adjusting ASAs to fix an out-of-adjustment brake is a dangerous practice 

that can have serious consequences. If an ASA is manually adjusted, the operator may 

wrongly assume the adjustment has “fixed” the braking problem, which gives the operator 

a false sense of security about the effectiveness of the braking system. The operator may 

believe that the brakes are fully reliable, when in fact they can go out of adjustment at any 

time, particularly in the case of vehicles that operate in hilly or mountainous 

environments. As the Glen Rock and El Cerrito accidents demonstrate, manually adjusting 

ASAs can create a situation in which brakes will not be capable of responding properly 

when they are desperately needed.

Insufficient Industry Awareness of the Risk Posed by Manually Adjusting 

ASAs. Although the CVSA’s Operation Air Brake data indicate that trucks with ASAs are 

placed out of service for out-of-adjustment brakes only half as frequently as those with 

brakes that have manual adjusters, ASA-equipped trucks are still being placed out of 

service for this deficiency, which suggests that ASAs have not solved the problem of outof-adjustment brakes. Lack of knowledge about ASAs is one reason for the continuing 

problem. Since the Glen Rock and El Cerrito accidents, Safety Board investigators have 

questioned a number of randomly selected mechanics on the practice of manually adjusting 

ASAs. The majority indicated that they manually adjust ASAs when they are out of 

adjustment, a practice that ASA manufacturers neither suggest nor endorse.

In addition, results of the driver survey conducted in 2000 by the OOIDA89 showed 

that a majority of drivers, particularly owner-operators, are performing brake adjustments 

89 “The Driver Perspective,” Report of Proceedings of the North American Brake Safety Conference, 

September 15-16, 2000.
Analysis 43 Highway Accident Report

on both manual slack adjusters and ASAs. The 2003 Operation Air Brake driver survey 

showed that about half of the drivers responding believed that ASAs never go out of 

adjustment and about one-third thought that a driver with proper tools could readjust 

ASAs. The Safety Board therefore concludes that the warnings in existing materials 

available to owners, drivers, mechanics, and inspectors of air-braked vehicles equipped 

with ASAs have not been successful in communicating the inherent dangers of manually 

adjusting ASAs to correct out-of-adjustment brakes. Operation Air Brake Committee 

members told Safety Board investigators that during the 2003 Operation Air Brake driver 

survey, drivers who obtained information about air brakes from manuals, rather than 

classroom training, their companies, or other truckers, knew more about the safe operation 

of air-braked vehicles and had fewer brake out-of-service violations.

Educational and maintenance materials regarding vehicle components should be 

based on manufacturers’ recommendations because manufacturers are in the best position 

to understand how their products work. The service manuals of ASA manufacturers 

provide instructions on how to troubleshoot for a brake with excessive pushrod stroke. 

None of the manufacturers recommends manual ASA adjustment as a means to correct 

this problem. Most of the manufacturers explicitly state in their literature that an ASA 

should not have to be manually adjusted except at the time of brake installation. 

Nevertheless, only one manufacturer (Haldex) indicates in its literature that manual 

adjustment should not be undertaken to correct out-of-adjustment brakes and that this 

condition requires brake system troubleshooting. The other manufacturers do not 

definitively state that adjusting an ASA is the wrong way to remedy excessive pushrod 

stroke.

The Safety Board believes that ASA manufacturers and marketers90 should revise 

their product literature to include conspicuously placed wording that clearly states that 

ASAs should not be manually adjusted in an effort to correct excessive pushrod stroke, 

because this condition indicates that a problem exists with the automatic adjuster, with the 

installation of the adjuster, or with related foundation brake components, which manual 

adjustment will not fix. Further, the literature should state that manual adjustment of 

ASAs is a dangerous practice that could have serious consequences, because it gives the 

operator a false sense of security about the effectiveness of the brakes, which are likely to 

go out of adjustment again soon.

In August 2004, a coalition of five ASA manufacturers endorsed and submitted to 

the AAMVA language about ASAs to be included in the AAMVA’s new model

Commercial Driver License Manual, which was distributed on January 3, 2006. The new 

manual includes language on manual adjustment of ASAs stating (in part) that ASAs 

should not have to be manually adjusted except during the installation of the ASAs and 

when performing brake maintenance. It also states that manual adjustment of an ASA to 

bring a brake pushrod stroke within legal limits is masking a mechanical problem, not 

fixing it, and that manual adjustment of most ASAs is likely to result in premature wear of 

the adjuster. Further, the new language states that manual adjustment of an ASA should be 

90 Including Bendix Spicer, which markets ASAs manufactured by Haldex.
Analysis 44 Highway Accident Report

used only in an emergency, as a temporary measure to correct the adjustment, because the 

brake will soon be back out of adjustment, given that manual adjustment will not fix the 

underlying braking problem.

The Safety Board commends both the ASA manufacturers and the AAMVA for 

adding this language to the model manual. However, the new language concerning ASAs 

omits one vital element. It should also state that the manual adjustment of ASAs is 

actually dangerous because it gives the operator a false sense of security about the 

effectiveness of the braking system. The Safety Board understands that the AAMVA 

revises the model Commercial Driver License Manual about every 10 years and the 2005 

version has already been distributed, so it is not possible to add this language to the current 

version. All 50 States use the information in the AAMVA model manual. Because the new 

model manual has only recently been distributed, the States probably have not yet been 

able to adopt it for their use. Therefore, to ensure that the State CDL manuals reflect the 

full range of risks posed by manual adjustment of ASAs, the Safety Board believes that 

when the 50 States and the District of Columbia incorporate the information on ASAs 

from the new AAMVA model Commercial Driver License Manual into their CDL 

manuals, they should include a statement that the manual adjustment of ASAs is 

dangerous because it gives the vehicle operator a false sense of security about the 

effectiveness of the braking system. In addition, the Safety Board will write a drop-in 

article for the AAMVA’s Move magazine. The article will explain that the States need to 

include material in their CDL manuals stating that manual adjustment of ASAs is a 

dangerous practice that can have serious consequences, because it gives the operator a 

false sense of security about the effectiveness of the brakes, which are likely to go out of 

adjustment again soon. 

The revision of the model CDL manual should help ensure that new CDL drivers 

are cautioned against manually adjusting ASAs, because drivers seeking CDLs usually 

use the manual to prepare for CDL qualification. However, the U.S. Department of Labor 

estimates that the total number of active CDL holders is about 2.9 million, and recent 

OOIDA and CVSA survey results suggest that a high proportion of experienced CDL 

drivers do not understand ASAs. In addition, about one-third of the brakes placed out of 

service for being out of adjustment have ASAs, which indicates that brake adjustment 

remains a serious maintenance and safety problem. As the Glen Rock, El Cerrito, and 

other accidents demonstrate, truck drivers, mechanics, and inspectors need to be better 

informed about the proper operation and maintenance of air brakes in general and ASAs in 

particular.

The CVSA has recognized the importance of air brake education and proper brake 

adjustment. It developed and, during the 2004 and 2005 Operation Air Brake campaigns, 

distributed a pamphlet entitled Air Brake Adjustment—Why is it so important? The 

pamphlet includes clear language warning that manually adjusting an ASA is a temporary 

way to bring a brake into compliance (with out-of-service adjustment limits) but will not 

fix the underlying problem. The Safety Board commends this effort and encourages the 

CVSA to give additional emphasis to this critical safety issue. The Safety Board believes 

that the CVSA should revise its pamphlet, Air Brake Adjustment—Why is it so important?,
Analysis 45 Highway Accident Report

to emphasize that the manual adjustment of ASAs is a dangerous practice that can have 

serious consequences, because it gives the operator a false sense of security about the 

effectiveness of the brakes, which are likely to go out of adjustment again soon. In 

addition, in a further effort to reach drivers, operators, mechanics, and others in the 

trucking industry, the Safety Board will write a drop-in article for Transport Topics, the 

magazine of the ATA, which has wide distribution in the general trucking industry. The 

article will include information about the risks associated with manually adjusting ASAs.

Some drivers and owners of vehicles equipped with air brakes may not interact 

with the CVSA, the FMSCA, or the ATA. They include fire departments, construction 

workers and companies, nursery and landscaping companies, and recreational vehicle 

owners. To reach these drivers and owners, the Safety Board will contribute drop-in 

articles on the risks associated with manually adjusting ASAs to industry, trade, and other 

groups, including the International Association of Fire Chiefs, the American Nursery and 

Landscape Association, the National Private Truck Council, the National Recreational 

Vehicle Owners Club, and the Associated General Contractors of America, for their 

publications. In addition, the CVSA air brake adjustment pamphlet could be distributed at 

campgrounds and recreational vehicle parks.

The ASE certifies brake repair and service professionals who maintain trucks, and 

its medium-heavy truck tests include test T4 for brakes. Given the widespread lack of 

awareness of the problems associated with manually adjusting ASAs in the trucking 

industry, the ASE should emphasize the risks associated with manually adjusting ASAs in 

its testing materials. As far as the Safety Board can determine, the T4 certification test 

does not currently address the manual adjustment of ASAs. Therefore, the Safety Board 

believes that the ASE should include the following information in its T4 brake 

certification testing materials: manually adjusting ASAs is dangerous and should not be 

done, except during installation or in an emergency to move the vehicle to a repair facility, 

because manual adjustment of this brake component (1) fails to address the true reason 

why the brakes are not maintaining adjustment, giving the operator a false sense of 

security about the effectiveness of the brakes, which are likely to go out of adjustment 

again soon, and (2) causes abnormal wear to the internal adjusting mechanism for most 

ASAs, which may lead to failure of this brake component.

The ASE does not publish study guides or manuals on its certification tests, but 

several companies do publish such guides.91 The Safety Board’s examination of several 

private study guides for the ASE’s medium-heavy truck T4 brake test showed that they 

inadequately cover the maintenance of ASA-equipped brakes, and some contain incorrect 

information. One study guide wrongly states, “Automatic slack adjusters may require 

periodic adjustment.” Many mechanics use the study guides as a source of general 

maintenance information, as well as for test preparation, making it imperative that these 

guides contain thorough and accurate information about ASAs. Therefore, the Board 

believes that the publishers of ASE certification test study guides should include the 

following information in their guides: manually adjusting ASAs is dangerous and should 

91 The leading publishers are Motor Age, Mitchell 1, and Thompson Delmar Learning.
Analysis 46 Highway Accident Report

not be done, except during installation or in an emergency to move the vehicle to a repair 

facility, because manual adjustment of this brake component (1) fails to address the true 

reason why the brakes are not maintaining adjustment, giving the operator a false sense of 

security about the effectiveness of the brakes, which are likely to go out of adjustment 

again soon, and (2) causes abnormal wear to the internal adjusting mechanism for most 

ASAs, which may lead to failure of this brake component.

Evidence from the Glen Rock accident suggests that some truck inspectors who 

carry out State annual inspections do not understand that if an ASA-equipped brake is out 

of adjustment, something is wrong with the adjuster or another foundation brake 

component and that manually adjusting the ASA merely masks the problem. Two different 

mechanics manually adjusted the ASAs on the Glen Rock accident truck several times. 

Both mechanics were Pennsylvania State-certified truck inspectors. Truck inspectors who 

perform annual inspections in the 23 other States (and the District of Columbia) that have 

State commercial vehicle inspection programs may be similarly unaware that manually 

adjusting ASAs is a dangerous and inappropriate response to an out-of-adjustment brake. 

Therefore, the Safety Board believes that the District of Columbia and the 24 States that 

have commercial vehicle inspection programs should include in their truck inspector 

training courses a module on ASAs that emphasizes that manually adjusting ASAs is 

dangerous and should not be done, except during installation or in an emergency to move 

the vehicle to a repair facility, because manual adjustment of this brake component (1) 

fails to address the true reason why the brakes are not maintaining adjustment, giving the 

operator a false sense of security about the effectiveness of the brakes, which are likely to 

go out of adjustment again soon, and (2) causes abnormal wear to the internal adjusting 

mechanism for most ASAs, which may lead to failure of this brake component.

During a Maryland roadside inspection on April 10, 2002, the Glen Rock accident 

truck was placed out of service for out-of-adjustment brakes. The driver at the time 

manually adjusted the brakes before departing the inspection site, an action that is not 

uncommon. The Safety Board found no indication that the brakes were subsequently 

examined to determine why they had gone out of adjustment. The inspector who conducted 

the roadside inspection evidently did not indicate that troubleshooting should be conducted 

to determine the underlying problem that was causing the brakes to be out of adjustment.

The CVSA has recognized the importance of air brake education and proper brake 

adjustment and has distributed materials informing drivers that manually adjusting an 

ASA will not remedy the underlying problem with an out-of-adjustment brake and is only 

a temporary fix; however, the CVSA North American Standard Inspection materials used 

to train roadside inspectors are silent on the subject. CVSA-trained roadside inspectors 

should be educated about the dangers of manually adjusting ASAs. The CVSA and the 

FMCSA National Training Center maintain the North American Standard Inspection 

training materials. Therefore, the Safety Board believes that the CVSA and the FMCSA 

should work together to develop and add to the North American Standard Inspection 

training materials a module that emphasizes that manually adjusting ASAs is dangerous 

and should not be done, except during installation or in an emergency to move the vehicle 

to a repair facility, because manual adjustment of this brake component (1) fails to address 
Analysis 47 Highway Accident Report

the true reason why the brakes are not maintaining adjustment, giving the operator a false 

sense of security about the effectiveness of the brakes, which are likely to go out of 

adjustment again soon, and (2) causes abnormal wear to the internal adjusting mechanism 

for most ASAs, which may lead to failure of this brake component.

Truck manufacturers’ manuals afford yet another means of improving industry 

awareness of the risks associated with manually adjusting ASAs. The Ford owner’s 

manual for a model 2003 F650/750, which is similar to the Glen Rock accident truck, 

states that ASAs should be checked for adjustment every 4 months, or 20,000 miles, and 

more frequently if operated in hilly or mountainous regions or in mud. It does not inform 

drivers or mechanics about the dangers involved in adjusting ASAs. The Safety Board, 

through the Truck Manufacturers Association, queried medium-heavy truck 

manufacturers to determine what information, if any, they provide regarding the manual 

adjustment of ASAs. Freightliner, the only manufacturer to respond to the inquiry, 

indicated that its manuals are silent on the subject. Freightliner advised Safety Board 

investigators that it will revise its driver, maintenance, and service manuals to include 

cautions about manually adjusting ASAs when it next updates its manuals.

To ensure that the manufacturers of vehicles equipped with air brakes provide 

appropriate guidance to vehicle operators, the Safety Board believes that the 

manufacturers should revise their product manuals to include conspicuously placed 

wording that clearly states that ASAs should not be manually adjusted in an effort to 

correct excessive pushrod stroke, because this condition indicates that a problem exists 

with the automatic adjuster, with the installation of the adjuster, or with related foundation 

brake components, which manual adjustment will not fix. Further, the product manuals 

should state that manual adjustment of ASAs is a dangerous practice that could have 

serious consequences, because it gives the operator a false sense of security about the 

effectiveness of the brakes, which are likely to go out of adjustment again soon.

Knowledge and Skills Needed to Drive Air Brake-Equipped Vehicles

Although the Glen Rock accident driver said that he slowed the truck before 

starting down the hill, he did not select a lower gear, which would have provided engine 

braking, an action recommended by the AAMVA model Commercial Driver License 

Manual and experienced truck drivers. Had he used a lower gear, the vehicle would have 

slowed due to normal engine compression. In addition, he pumped the brakes, reducing 

the capability of the front brakes and exacerbating the loss of braking capability in the outof-adjustment rear brakes. Until recent widespread use of ABS brakes, drivers of 

hydraulically braked vehicles (passenger cars, sport utility vehicles, and pickups and other 

light-duty trucks) were taught to pump their brakes in emergencies.92 But in an air-braked 

vehicle, pumping the brakes depletes the air pressure, thereby drastically reducing the 

brakes’ capability.

92 Although ABS brakes were introduced in the 1970s, they were not widely used until the 1990s. ABS 

brakes are designed to help prevent a vehicle from skidding. The brakes are controlled by a computer that 

senses whether the tires are maintaining friction with the pavement or are sliding. For ABS brakes, steady 

brake pedal pressure is prescribed. Pumping the brake pedal defeats the purpose of ABS.
Analysis 48 Highway Accident Report

The Glen Rock accident driver did not hold a CDL and he had not passed an air 

brake knowledge test; neither was required by regulation for him to drive the accident truck. 

The Glen Rock accident truck had a GVWR of 26,000 pounds and, for CDL licensing 

purposes, 49 CFR 383.5 defines a commercial vehicle as a motor vehicle that has a GVWR 

of 26,001 pounds or more. Consequently, the accident driver was not required to have a CDL 

to drive the accident truck. According to his statement, the driver had never received 

instruction on air brake operation. Also, although a road test is required by regulation, the 

motor carrier had not given the driver such a test in the accident truck. The accident driver 

said that he had been told that if the brake light came on, he had no [air] pressure, but it is not 

clear whether he understood what this meant. Therefore, the Safety Board concludes that the 

Glen Rock accident driver lacked the knowledge and skills required to safely drive an air 

brake-equipped vehicle; as a result, he did not select a lower gear before proceeding down 

the hill and he pumped the brakes, which depleted the available brake air pressure.

Air brakes and hydraulic brakes operate differently. Because of these differences, 

drivers of air-braked vehicles need special instruction about how they function. In the 

United States, licensed drivers who do not hold CDLs are not typically given information 

about the operation of air brake systems, and they are not tested about air brakes before 

they are permitted to drive vehicles equipped with them. In contrast, the CDL licensing 

program recognizes that drivers need to be aware of the special characteristics of air brake 

systems and has established knowledge and skill requirements for operating them safely.

The AAMVA model Commercial Driver License Manual contains a section that 

specifically addresses air brake knowledge. If a CDL applicant wants to be licensed to drive 

an air brake-equipped vehicle, the applicant is required93 to take a separate knowledge test and 

demonstrate proficiency in the inspection and operation of air brake systems. If a CDL 

applicant fails to pass the air brake knowledge and skills tests, the applicant is prohibited from 

driving vehicles with air brake systems. However, a non-CDL driver is not restricted from 

driving an air brake-equipped vehicle, whether in commercial or noncommercial use. Thus, 

no measures are in place to ensure that the drivers of air brake-equipped vehicles weighing 

less than 26,000 pounds have the knowledge and skills necessary for their safe operation.

Canada has recognized the importance of air brake system proficiency in its 

licensing system. Since 2001, Transport Canada has required that all drivers who drive 

any vehicle equipped with air brakes obtain an air brake endorsement. Transport Canada 

reports that Canada has experienced a reduction in brake-related accidents since the 

adoption of this requirement. Also, between September 1999 and September 2004, 

Canada experienced a 25-percent reduction in brakes found to be out of adjustment to the 

point of being out of service.94

U.S. accident statistics show that about one-third of straight truck accidents 

involve drivers who do not have CDLs.95 Studies suggest that a significant portion of these 

93 Title 49 CFR 383.95 and 383.113(c).

94 From Operation Air Brake data for 1999 through 2004.

95 Matteson and Blower, Trucks Involved in Fatal Accidents Factbook 2000.
Analysis 49 Highway Accident Report

accidents involve braking problems.96 Data from the 2002 vehicle inventory and use 

survey97 indicate that at least 30 percent (516,110) of trucks in the 19,501- to 26,000-

pound weight class are equipped with air brakes. In addition, Freightliner and 

International data for new vehicles indicate that about 80 percent and 40 percent, 

respectively, of these manufacturers’ new vehicles in this weight class are equipped with 

air brakes. These vehicles are in operation today (both in commercial and noncommercial 

use), and drivers without CDLs may legally operate them. Therefore, the Safety Board 

concludes that more than 500,000 vehicles equipped with air brakes may be operated by 

drivers who, like the Glen Rock truck driver, have no air brake training and thus may not 

be able to operate their vehicles safely.

To summarize, under the CDL program, each State has an air brake testing 

requirement, information in its CDL manual concerning air brakes, and a test for air brake 

systems. However, non-CDL drivers are not required to fulfill any air brake knowledge or 

testing requirement before driving an air brake-equipped vehicle. Further, a CDL is not 

required to drive a commercial vehicle with a GWVR of 26,000 pounds or less. So two 

major categories of drivers—commercial drivers who are not required to hold CDLs and 

noncommercial drivers—may not receive any air brake training or testing before they 

drive air brake-equipped vehicles.

As this accident demonstrates, all drivers should receive specialized training in 

using air brakes before driving a vehicle equipped with them. The FMCSA regulates 

commercial vehicle operations and commercial driver licensing. Therefore, the Safety 

Board believes that the FMCSA should require drivers of commercial vehicles that weigh 

less than 26,000 pounds and are equipped with air brakes to undergo training and testing 

to demonstrate proficiency in the inspection and operation of air-braked vehicles; the 

training should emphasize that manually adjusting ASAs is dangerous and should not be 

done, except during installation or in an emergency to move the vehicle to a repair facility. 

Further, to address the issue of untrained noncommercial drivers driving air brakeequipped vehicles, the Safety Board believes that the 50 States and the District of 

Columbia should adopt an air brake endorsement for drivers’ licenses that would require 

training and testing of drivers who drive air brake-equipped vehicles to ensure their 

proficiency in the operation of air-braked vehicles; the training should emphasize that 

manually adjusting ASAs is dangerous and should not be done, except during installation 

or in an emergency to move the vehicle to a repair facility. Currently, the States are 

equipped to provide air brake testing for CDL drivers who wish to remove the air brake 

restriction from their licenses. The States could extend such testing to commercial drivers 

of vehicles that weigh less than 26,000 pounds and are equipped with air brakes, as well as 

to noncommercial drivers who drive air-braked vehicles. In addition, 32 States have a 

classified license system, which should facilitate the implementation of air brake 

knowledge and skills testing for noncommercial drivers.

96 GAO-03-436, March 2003, and FMCSA-PSV-04-001, December 2003.

97 The Safety Board analyzed the raw data from the 2002 Economic Census, Vehicle Inventory and Use 

Survey, using the GVWR information from the Vehicle Identification Numbers.
Analysis 50 Highway Accident Report

Motor Carrier Oversight

Blossom Valley

Blossom Valley employed a driver who had no experience driving air brakeequipped vehicles, did not train him in air brake use or pretrip inspection, and put him on the 

road in an air brake-equipped vehicle with out-of-adjustment rear brakes. In addition, the 

truck was loaded beyond its rated weight, and the driver was dispatched on a route that 

included a section of road the vehicle was not permitted to be on even when empty. 

(Apparently, the carrier ignored this routing prohibition after the accident as well. On 

March 10, 2004, another Blossom Valley truck was ticketed for traveling overweight down 

Church Street.) Moreover, the carrier did not have a scheduled maintenance program for its 

vehicles, did not have a drug and alcohol testing program, and did not maintain driver 

qualification files or keep time records on its drivers, all of which the FMCSA requires 

motor carriers to do. The Safety Board concludes that Blossom Valley did not exercise 

proper oversight of its drivers, vehicles, or operation, as evidenced by its sending an 

untrained truck driver in an overloaded vehicle with out-of-adjustment brakes on a route 

over a weight-restricted street; the carrier also failed to implement a scheduled vehicle 

maintenance program and to fulfill drug and alcohol testing and record-keeping 

requirements. In 2005, Blossom Valley Farms, Inc., in Pennsylvania was sold, and the new 

nursery does not make deliveries.

Educating Motor Carriers

The owner of Blossom Valley knew enough about motor carrier operational 

requirements to register with the USDOT. To obtain operating authority, the owner had to 

sign an FMCSA Form 150, Motor Carrier Identification Report (application for a USDOT 

number), which contains a statement indicating that the carrier understands the FMCSRs 

(and/or the Federal Hazardous Materials Regulations). However, Blossom Valley’s owner 

told investigators that, before the accident, he was unaware of the FMCSRs’ requirements 

as they applied to Blossom Valley operations. Consequently, the carrier did not adhere to 

the FMCSRs.

The FMCSA has taken steps to educate carriers about their responsibilities under 

the FMCSRs. For instance, since January 1, 2003, all new motor carriers (private and forhire) operating in interstate commerce must apply for registration (obtain a USDOT 

number) as a “new entrant.” According to the FMCSA,98 after the carrier receives its new 

entrant registration, it is subject to an 18-month-long safety-monitoring period, during 

which it will receive a safety audit and have its roadside crash and inspection information 

closely evaluated. The carrier will be required to demonstrate that it has the necessary 

systems in place to ensure basic safety management controls. Failure to do so may result in 

the carrier having its new entrant registration revoked. In FY 2003–2004, the FMCSA and 

the States, respectively, conducted 7,205 and 25,316 new entrant safety audits. Blossom 

Valley had registered with the USDOT in 1987, about 16 years before the FMCSA’s new 

entrant program was implemented and so was not subject to a safety-monitoring period.

98 See <http://www.fmcsa.dot.gov/registration-licensing/registration/new-entrant.htm>.
Analysis 51 Highway Accident Report

The FMCSA’s compliance monitoring activities can also be helpful in instructing 

carriers about their responsibilities, because FMCSA inspectors generally treat a first 

compliance review as an educational visit. However, recent compliance monitoring 

activity indicates that the FMCSA and the States together conduct only about 11,300 

compliance reviews each year. In FY 2004, active interstate truck and bus companies 

numbered 677,249, many of which were unrated carriers. Thus, FMCSA compliance 

activities affecting unrated carriers are limited and may not serve to educate many small, 

private motor carriers about the requirements they must meet. In fact, the FMCSA had not 

conducted a compliance review of Blossom Valley before the accident (nor assigned it a 

safety rating), so Blossom Valley was an unrated carrier, and this program did not enhance 

the carrier’s understanding of its responsibilities under Federal regulations.

The FMCSA also has educational material on its Web site, including a link to A 

Motor Carrier’s Guide to Improving Highway Safety. This booklet provides information 

for commercial vehicle owners unfamiliar with the FMCSA and addresses the Federal 

regulations applicable to commercial vehicle operation.

Despite the FMCSA’s educational efforts, Blossom Valley was evidently unaware of, 

and failed to fulfill, its responsibilities as a motor carrier under the FMCSRs. Given Blossom 

Valley’s deficient understanding of its responsibilities as a motor carrier, the Safety Board 

concludes that the FMCSA’s efforts to educate motor carriers about their responsibilities 

under Federal safety regulations have not reached all small, private, unrated carriers.

The Safety Board recently issued a report on an accident in Tallulah, Louisiana,99

involving a motorcoach operated by a church group that did not realize it qualified as a 

motor carrier under Federal regulations. As a result of the October 13, 2003, accident, 

eight motorcoach passengers sustained fatal injuries, and the motorcoach driver and six 

passengers received serious injuries. On April 27, 2005, the Safety Board issued the 

following safety recommendation to the FMCSA:

H-05-2

Develop and distribute educational materials for nontraditional commercial 

vehicle owners, such as church groups, on how to comply with the Federal 

Motor Carrier Safety Regulations; at a minimum, the materials should be 

posted on the Federal Motor Carrier Safety Administration Web site.

The category “nontraditional commercial vehicle owners” includes small, private 

carriers such as Blossom Valley, and vigorous implementation of this recommendation 

may improve compliance with the FMCSRs on the part of such carriers. In a letter dated 

September 30, 2005, the FMCSA responded to Safety Recommendation H-05-2, 

indicating that it is “developing an educational brochure to increase the safety awareness 

and regulatory compliance of private motor carriers of passengers.” The Safety Board is 

reviewing the response.

99 National Transportation Safety Board, Motorcoach Run-Off-The-Road Accident, Tallulah, Louisiana, 

October 13, 2003, Highway Accident Report NTSB/HAR-05/01 (Washington, DC: NTSB, 2005).
Analysis 52 Highway Accident Report

FMCSA Carrier Safety Rating Systems

On April 10, 2002, about 1 year before this accident, the accident truck underwent 

a CVSA level 1 roadside inspection and was placed out of service. This roadside 

inspection was the only one conducted on a Blossom Valley vehicle in 2002, so the 

FMCSA’s SafeStat records showed the carrier with a 100-percent out-of-service rate for 

the year. However, the ISS-2 data for the carrier would not have included Blossom 

Valley’s out-of-service rate because the carrier had not undergone a FMCSA compliance 

review during its 16 years of operation; consequently, the system considered Blossom 

Valley “not rated.” Thus, Blossom Valley would have had an ISS-2 inspection value of 65 

(inspection optional) a few weeks before the accident, based on “insufficient information,” 

because the carrier had not undergone a compliance review and was unrated at the time.

A postaccident ISS-2 query for Blossom Valley conducted on September 19, 2003, 

indicated that the carrier’s inspection value was 82 (inspection warranted), as a result of 

the carrier’s postaccident compliance review safety rating of “Conditional,” which derived 

from an “Unsatisfactory” rating in the vehicle factor. Since the Glen Rock accident, two 

Blossom Valley vehicles have undergone roadside inspections that resulted in out-ofservice vehicles, maintaining the carrier’s 100-percent out-of-service rate, and Blossom 

Valley’s safety rating remains “Conditional.” However, because the ISS-2 system 

automatically reduces an infraction score over time, a September 23, 2005, ISS-2 query 

indicated that the carrier’s inspection value was 73, placing it in the “inspection optional” 

category even though nothing about its safety posture had changed. The SafeStat system 

still showed the carrier with an out-of-service rate of 100 percent, and the compliance 

review rating was still “Conditional.” The ISS-2 system gives the carrier the benefit of the 

doubt and assumes it will improve its safety standing, regardless of whether it does so. 

The Safety Board therefore concludes that the FMCSA’s ISS-2 system does not always 

give an accurate and timely picture of a carrier’s safety posture, thereby reducing its 

effectiveness as a screening mechanism.

The Safety Board understands that, in response to a recent USDOT, Office of the 

Inspector General, report,100 the FMCSA is making changes to the SafeStat and ISS-2 

systems. The Safety Board’s report of the June 23, 2002, Victor, New York, motorcoach 

accident101 thoroughly discussed the inadequacies of SafeStat and the ISS-2 system, as 

well as the Inspector General’s recommendations.

The facts about Blossom Valley’s FMCSA safety rating uncovered during the Glen 

Rock investigation underscore the Safety Board’s concerns, expressed in the Victor report, 

about the limitations of the FMCSA’s safety rating systems for motor carriers. The 

comparatively positive inspection value that Blossom Valley continues to maintain in the 

ISS-2 system, despite the carrier’s clear safety inadequacies, emphasizes the need for the 

FMCSA to improve its carrier safety rating systems.

100 U.S. Department of Transportation, Office of the Inspector General, Improvements Needed in the Motor 

Carrier Safety Status Measurement System, Audit Report MH-2004-034 (Washington, DC: USDOT, 2004).

101 National Transportation Safety Board, Motorcoach Run-off-the-Road and Rollover Off Interstate 90, 

Victor, New York, June 23, 2002, Highway Accident Report NTSB/HAR-04/03 (Washington, DC: NTSB, 

2004).
53 Highway Accident Report

Conclusions

Findings

1. Although the highway’s design included a steep grade, it was appropriately signed 

and, therefore, was not a factor in the accident; also, the emergency response was 

effective and appropriate.

2. Based on the truck driver’s statements about pumping the brakes, postaccident 

examination of the brakes, and results from computer simulations, the accident truck 

did not have sufficient braking capability to stop before the initial impact with the 

stopped cars.

3. Although it cannot be determined if drugs or fatigue impaired the driver’s 

performance, he most likely could not have stopped the truck before the accident 

occurred.

4. At the time of the accident, the automatic slack adjusters for all four of the accident 

truck’s brakes were capable of working properly; however, the quick-connect clevises 

and clevis pins for both rear brakes were worn to the extent that they prevented the 

automatic slack adjusters from properly adjusting the brakes, thereby reducing the 

capability of the rear brakes.

5. The drivers and mechanics who manually adjusted the automatic slack adjusters on 

the trucks involved in the Glen Rock and El Cerrito accidents did not look for 

underlying problems with the adjusters or related foundation brake components; 

consequently, they misdiagnosed the brake problems, probably because they were not 

properly educated on the function and care of automatic slack adjusters and how they 

relate to foundation brake systems.

6. The warnings in existing materials available to owners, drivers, mechanics, and 

inspectors of air-braked vehicles equipped with automatic slack adjusters have not 

been successful in communicating the inherent dangers of manually adjusting 

automatic slack adjusters to correct out-of-adjustment brakes.

7. The Glen Rock accident driver lacked the knowledge and skills required to safely 

drive an air brake-equipped vehicle; as a result, he did not select a lower gear before 

proceeding down the hill and he pumped the brakes, which depleted the available 

brake air pressure.

8. More than 500,000 vehicles equipped with air brakes may be operated by drivers 

who, like the Glen Rock truck driver, have no air brake training and thus may not be 

able to operate their vehicles safely.
Conclusions 54 Highway Accident Report

9. Blossom Valley Farms, Inc., did not exercise proper oversight of its drivers, vehicles, 

or operation, as evidenced by its sending an untrained truck driver in an overloaded 

vehicle with out-of-adjustment brakes on a route over a weight-restricted street; the 

carrier also failed to implement a scheduled vehicle maintenance program and to 

fulfill drug and alcohol testing and record-keeping requirements.

10. The Federal Motor Carrier Safety Administration’s efforts to educate motor carriers 

about their responsibilities under Federal safety regulations have not reached all 

small, private, unrated carriers.

11. The Federal Motor Carrier Safety Administration’s Inspection Selection System does 

not always give an accurate and timely picture of a carrier’s safety posture, thereby 

reducing its effectiveness as a screening mechanism.

Probable Cause

The National Transportation Safety Board determines that the probable cause of 

this accident was the lack of oversight by Blossom Valley Farms, Inc., which resulted in 

an untrained driver improperly operating an overloaded, air brake-equipped vehicle with 

inadequately maintained brakes. Contributing to the accident was the misdiagnosis of the 

truck’s underlying brake problems by mechanics involved with the truck’s maintenance; 

also contributing was a lack of readily available and accurate information about automatic 

slack adjusters and inadequate warnings about the safety problems caused by manually 

adjusting them.
55 Highway Accident Report

Recommendations

As a result of its investigation, the National Transportation Safety Board makes the

following safety recommendations:

To the Federal Motor Carrier Safety Administration:

Work with the Commercial Vehicle Safety Alliance to develop and add to

the North American Standard Inspection training materials a module that

emphasizes that manually adjusting automatic slack adjusters is dangerous

and should not be done, except during installation or in an emergency to

move the vehicle to a repair facility, because manual adjustment of this

brake component (1) fails to address the true reason why the brakes are not

maintaining adjustment, giving the operator a false sense of security about

the effectiveness of the brakes, which are likely to go out of adjustment

again soon, and (2) causes abnormal wear to the internal adjusting

mechanism for most automatic slack adjusters, which may lead to failure of

this brake component. (H-06-1)

Require drivers of commercial vehicles that weigh less than 26,000 pounds

and are equipped with air brakes to undergo training and testing to

demonstrate proficiency in the inspection and operation of air-braked

vehicles; the training should emphasize that manually adjusting automatic

slack adjusters is dangerous and should not be done, except during installation

or in an emergency to move the vehicle to a repair facility. (H-06-2)

To the District of Columbia and the 50 States:

When you incorporate the information on automatic slack adjusters from

the new American Association of Motor Vehicle Administrators model

Commercial Driver License Manual into your Commercial Driver’s

License manual, include a statement that the manual adjustment of automatic

slack adjusters is dangerous because it gives the vehicle operator a false

sense of security about the effectiveness of the braking system. (H-06-3)

Adopt an air brake endorsement for drivers’ licenses that would require

training and testing of drivers who drive air brake-equipped vehicles to

ensure their proficiency in the operation of air-braked vehicles; the training

should emphasize that manually adjusting automatic slack adjusters is

dangerous and should not be done, except during installation or in an

emergency to move the vehicle to a repair facility. (H-06-4)
Recommendations 56 Highway Accident Report

To the District of Columbia and the 24 States (Alabama, Arkansas, California, 

Connecticut, Hawaii, Illinois, Louisiana, Maine, Maryland, Michigan, Minnesota, 

New Hampshire, New Jersey, New York, Ohio, Oklahoma, Pennsylvania, Rhode 

Island, Texas, Utah, Vermont, Virginia, West Virginia, and Wisconsin) that have 

commercial vehicle inspection programs:

Include in your truck inspector training courses a module on automatic 

slack adjusters that emphasizes that manually adjusting automatic slack 

adjusters is dangerous and should not be done, except during installation or 

in an emergency to move the vehicle to a repair facility, because manual 

adjustment of this brake component (1) fails to address the true reason why 

the brakes are not maintaining adjustment, giving the operator a false sense 

of security about the effectiveness of the brakes, which are likely to go out 

of adjustment again soon, and (2) causes abnormal wear to the internal 

adjusting mechanism for most automatic slack adjusters, which may lead to 

failure of this brake component. (H-06-5)

To the Commercial Vehicle Safety Alliance:

Revise your pamphlet, Air Brake Adjustment—Why is it so important?, to 

emphasize that the manual adjustment of automatic slack adjusters is a 

dangerous practice that can have serious consequences, because it gives the 

operator a false sense of security about the effectiveness of the brakes, 

which are likely to go out of adjustment again soon. (H-06-6)

Work with the Federal Motor Carrier Safety Administration to develop and 

add to the North American Standard Inspection training materials a module 

that emphasizes that manually adjusting automatic slack adjusters is 

dangerous and should not be done, except during installation or in an 

emergency to move the vehicle to a repair facility, because manual 

adjustment of this brake component (1) fails to address the true reason why 

the brakes are not maintaining adjustment, giving the operator a false sense 

of security about the effectiveness of the brakes, which are likely to go out 

of adjustment again soon, and (2) causes abnormal wear to the internal 

adjusting mechanism for most automatic slack adjusters, which may lead to 

failure of this brake component. (H-06-7)

To Haldex Brake Products Corporation, Bendix Commercial Vehicle Systems LLC, 

Bendix Spicer Foundation Brake LLC, Gunite Corporation, ArvinMeritor, Inc., and 

Crewson Industries, Inc. (manufacturers and marketers of automatic slack 

adjusters):

Revise your product literature to include conspicuously placed wording 

that clearly states that automatic slack adjusters should not be manually 

adjusted in an effort to correct excessive pushrod stroke, because this 

condition indicates that a problem exists with the automatic adjuster, with 

the installation of the adjuster, or with related foundation brake 

components, which manual adjustment will not fix. Further, the literature 
Recommendations 57 Highway Accident Report

should state that manual adjustment of automatic slack adjusters is a 

dangerous practice that could have serious consequences, because it gives 

the operator a false sense of security about the effectiveness of the brakes, 

which are likely to go out of adjustment again soon. (H-06-8)

To Freightliner LLC, Mack Trucks, Inc., International Truck and Engine Corporation, 

Kenworth Truck Company, Peterbilt Motors Company, Volvo Trucks North America, 

Inc., Ford Motor Company, General Motors Corporation, Hino Motor Sales U.S.A., 

Inc., and Nissan Diesel America Incorporated (manufacturers of vehicles equipped 

with air brakes):

Revise your product manuals to include conspicuously placed wording that 

clearly states that automatic slack adjusters should not be manually 

adjusted in an effort to correct excessive pushrod stroke, because this 

condition indicates that a problem exists with the automatic adjuster, with 

the installation of the adjuster, or with related foundation brake 

components, which manual adjustment will not fix. Further, the product 

manuals should state that manual adjustment of automatic slack adjusters is 

a dangerous practice that could have serious consequences, because it gives 

the operator a false sense of security about the effectiveness of the brakes, 

which are likely to go out of adjustment again soon. (H-06-9)

To the National Institute for Automotive Service Excellence:

Include the following information in your T4 brake certification testing 

materials: manually adjusting automatic slack adjusters is dangerous and 

should not be done, except during installation or in an emergency to move 

the vehicle to a repair facility, because manual adjustment of this brake 

component (1) fails to address the true reason why the brakes are not 

maintaining adjustment, giving the operator a false sense of security about 

the effectiveness of the brakes, which are likely to go out of adjustment 

again soon, and (2) causes abnormal wear to the internal adjusting 

mechanism for most automatic slack adjusters, which may lead to failure of 

this brake component. (H-06-10)

To Motor Age, Mitchell 1, and Thompson Delmar Learning (publishers of National 

Institute for Automotive Service Excellence certification test study guides):

Include the following information in your National Institute for 

Automotive Service Excellence study guides: manually adjusting 

automatic slack adjusters is dangerous and should not be done, except 

during installation or in an emergency to move the vehicle to a repair 

facility, because manual adjustment of this brake component (1) fails to 

address the true reason why the brakes are not maintaining adjustment, 

giving the operator a false sense of security about the effectiveness of the 

brakes, which are likely to go out of adjustment again soon, and (2) causes 
Recommendations 58 Highway Accident Report

abnormal wear to the internal adjusting mechanism for most automatic slack 

adjusters, which may lead to failure of this brake component. (H-06-11)

BY THE NATIONAL TRANSPORTATION SAFETY BOARD

MARK V. ROSENKER

Acting Chairman

DEBORAH A. P. HERSMAN

Member

ELLEN ENGLEMAN CONNERS

Member

KATHRYN O’LEARY HIGGINS

Member

Adopted: February 7, 2006
59 Highway Accident Report

Appendix A

Investigation

The National Transportation Safety Board was notified of the Glen Rock, 

Pennsylvania, accident on April 11, 2003. The Safety Board dispatched an investigative 

team on April 16, 2003, which included members from the Parsippany, New Jersey; 

Denver, Colorado; and Gardena, California, offices. Groups were established to 

investigate highway and vehicle factors, as well as motor carrier operations.

Participating in the investigation were representatives of the Federal Motor Carrier 

Safety Administration, the Pennsylvania Department of Transportation, the Pennsylvania 

State Police, the Southern Regional Police Department, and the Gunite Corporation.
60 Highway Accident Report

Appendix B

Results of Safety Board Computer Simulations of Accident 

Events

Sim. 

no. 

Initial 

speed 

(mph) 

In 

gear 

(Y/N) 

Brake 

forces 

(drag or 

pulse) 

Time 

10 to 

15 

(psi) 

Time 

30 

(psi) 

Time 

50 

(psi) 

Highest 

speed 

(mph) 

Lowest 

speed 

(mph) 

Able to 

stop 

(speed 

end) 

Length 

sim. 

(sec.) 

Brake 

drum 

temp. 

(°F) 

Brake 

lining 

temp. 

(°F) 

1 1 Y Drag 12 75.2 77.7 27 0 Y 92.7 737 485 

2 1 Y Drag 12 65.2 67.7 26 0 Y 82.4 676 438 

3 1 Y Drag 12 65.2 67.7 26 0 Y 81.7 669 430 

4 1 Y Drag 22 85.2 -- 26 1 N (30) 86.2 588 399 

5 1 Y Drag 32 80.5 -- 27 1 N (33) 81.8 546 358 

6 1 Y Drag 32 -- -- 37 1 N (37) 73 540 323 

7 1 Y Drag 32 -- 72 37 1 N (36) 73 516 320 

8 25 Y Drag 3 79.3 81.8 27 16 N (16) 87.7 761 500 

9 25 Y Drag 3 69.3 71.8 26 0 Y 85.1 763 506 

10 25 Y Drag 3 59.3 61.8 27 0 Y 75.2 707 458 

11 25 Y Drag 3 50.5 53 27 0 Y 66.6 656 417 

12 25 Y Drag 3 40.5 43 27 0 Y 56.6 595 370 

13 25 Y Drag 21 55.3 57.8 37 21 N (21) 67.4 768 408 

14 25 Y Drag 39.5 50.5 53 48 25 N (40) 58.2 550 259 

15 25 Y Drag 38 49 51.5 47 25 N (35) 59.1 638 289 

16 35 Y Drag 3 40.5 43 40 0 Y 54.7 918 552 

17 35 Y Drag 3 30.5 33 38 0 Y 53.9 838 489 

18 35 Y Drag 3 20.5 23 38 0 Y 42.9 733 415 

19 35 Y Drag 3 50.5 53 39 27 N (27) 60.6 850 474 

20 35 Y Drag 3 53.5 56 39 34 N (34) 59.8 746 446 

21 45 Y Drag 3 38 40.5 53 45 N (47) 45.4 771 401 

22 45 Y Drag 3 28 30.5 51 17 N (17) 53.2 1170 642 

23 45 Y Drag 3 34.5 37 52 34 N (36) 46.7 1012 489 

24 55 Y Drag 3 34.5 37 59 53 N (53) 39.2 817 402 

25 55 Y Drag 3 25.5 28 58 34 N (34) 42.1 1177 549 

26 55 Y Drag 3 26 28.5 58 35 N (35) 41.8 1158 536 

27 25 N None -- -- -- 70 25 N (70) 46.6 150 150 

28 1 N None -- -- -- 67 1 N (67) 63.9 150 150 

29 1 Y/N None Neutral at 11.6 sec 67 1 N (67) 61.9 150 150 

30 1 Y Pulse 12 32 -- 28 0 Y 80.1 570 416 

31 1 Y Pulse 12 32 (pump 

down) 

31 1 N (31) 119.6 573 504 

32 1 Y Pulse 12 32 (pump 

down) 

30 1 N (30) 118 543 480 

33 1 Y Pulse 12 32 (pump 

down) 

36 1 N (36) 111.4 488 431 

34 25 Y Pulse 3 Pumped 

down to 0 

36 25 N (36) 75.6 466 356 

35 25 Y Pulse 3 Pumped 

down to 0 

35 25 N (35) 75.6 456 349 
61 Highway Accident Report

Appendix C

CVSA Pamphlet Air Brake Adjustment—Why is it so important?

Commercial Vehicle 

Safety Alliance

www.cvsa.org

1101 17th Street, N.W., Suite 803

Washington, DC 20036

Phone: 202-775-1623 • Fax: 202-775-1624 • www.cvsa.org

Safety Security

Promoting

Commercial Motor Vehicle

Safety and Security

Air Brake

ADJUSTMENT

Why is it so important?

CONTACTS

For information about commercial motor vehicle 

safety & security or to inquire about inspection 

training needs for law enforcement and industry

Commercial Vehicle Safety Alliance (CVSA)

1101 17th Street NW 

Suite 803

Washington, DC 20036

(202) 775-1623

www.cvsa.org

For further information about commercial motor

vehicle safety in the U.S.

Federal Motor Carrier Safety Administration (FMCSA)

Office of Bus and Truck Standards and Operations

400 Seventh Street SW

Washington, DC 20590

(202) 366-1790

www.fmcsa.dot.gov

For further information about commercial motor

vehicle safety in Canada

Canadian Council of Motor Transport 

Administrators (CCMTA)

2323 St. Laurent Boulevard

Ottawa, Ontario, Canada K1G 4J8

(613) 736-1003

www.ccmta.ca

For further information about commercial motor

vehicle safety in Mexico

Autotransporte Federal

Secretaría de Comunicaciones y Transportes (SCT)

Czda. de las Bombas, No. 411

Coyoacan, DF Ciudad de Mexico 04920

52-55-56841514

www.sct.gob.mx
Refer to the chart below to identify the adjustment limit of

each brake. Any brake that is stroking over its adjustment limit

is “out of adjustment.”

Why It’s So Helpful To Have Stroke 

Indicators On Your Brakes

There are devices to help you measure pushrod stroke. Visual

“stroke indicators” can be installed onto each brake to provide

a moving pointer that strokes with the brake. Some stroke

indicators will help you identify exactly where the adjustment

limit is and whether the stroke is under or over it. Others

only provide a convenient way to measure the stroke.

Checking brake adjustment generally means you have to get

under the vehicle and take measurements. Using certain types of

stroke indicators makes this job much easier. You can get accurate

measurements without having to crawl under the vehicle.

What To Do When Your Brakes Are Out 

Of Adjustment

When your brakes are out of adjustment, what you do about it

depends on whether your vehicle has manual or automatic

brake adjusters.

How To Tell When Your Brakes Are Out 

Of Adjustment

Brake adjustment is all about pushrod stroke. There’s only one

way to tell when you’ve got a brake adjustment problem. You’ve

got to “measure the stroke.”

The parts inside a brake chamber can only stroke so far

before the brake chamber “bottoms out.” When that happens,

the brake chamber doesn’t produce any more force on the

brakes. To prevent chamber “bottom out,” a brake’s stroke must

never be longer than its “adjustment limit.”

You need to measure to be sure your brakes are properly

adjusted and adjustment limits are different for each size and

type of brake chamber. So, you need to know the size and type

of brake chambers on each vehicle you’re operating as well as

their adjustment limit.

You can get information about the size and type of 

brake chambers on a vehicle from a technician, a dealer or 

your employer.

What About “Free-Stroke” & “Slack”

The distance you can pull the brake by hand using a bar or lever

is called its “slack” or “free-stroke.” This distance is generally 3/8

to 3/4 inch. You may get some indication of adjustment levels,

but you can’t really confirm proper brake adjustment this way.

Measuring “free-stroke” or “slack” doesn’t provide an accurate

indication of brake adjustment.

How To “Measure The Stroke” Properly

Before doing anything, block the wheels, release the spring

brakes and have a good look at the brakes. Each brake must be

in its normal released position. Make sure nothing is obviously

wrong or out of place. If your vehicle doesn’t have stroke

indicators, you’ll have to mark each pushrod.

Now, to “measure the stroke” properly, you’ll need to keep

the spring brakes released, make sure your air pressure gauges

show that you have 90 to 100 psi in the air tanks, shut the engine

off and then make a full service brake application. You must have

some way to hold the brake pedal down for this step.

You must measure how far each brake has stroked. Often an

estimate will do, but any brake that is close to the adjustment

limit must be carefully measured.

Adjustment limits for clamp-type brake chambers

Check stroke with 90-100 psi in tanks and brakes fully applied

SIZE MARKING OUTSIDE DIAMETER ADJUSTMENT LIMIT

6 none 4 1/2” (115mm) 1 1/4” (32mm)

9 none 5 1/4” (133mm) 1 3/8” (35mm)

12 none 5 11/16” (144mm) 1 3/8” (35mm)

16 none 6 3/8” (162mm) 1 3/4” (45mm)

16LS Square Ports, Tag & 6 3/8” (162mm) 2” (51mm)

Marking

20 none 6 25/32” (172mm) 1 3/4” (45mm)

20LS Square Ports, Tag & 6 25/32” (172mm) 2” (51mm)

Marking

24 none 7 7/32” (183mm) 1 3/4” (45mm)

24L ‘L’ and Stroke Tag 7 7/32” (183mm) 2” (51mm)

24LS Square Ports, Tag & 7 7/32” (183mm) 2 1/2” (64mm)

Marking

30 none 8 3/32” (205mm) 2” (51mm)

30 ‘DD3’ (Bus/Coach) 8 1/8” (206mm) 2 1/4” (57mm)

30LS Square Ports, Tag & 8 3/32” (205mm) 2 1/2” (64mm)

Marking

36 none 9” (228mm) 2 1/4” (57mm)

Appendix C 62 Highway Accident Report
READJUSTING MANUAL BRAKE

ADJUSTERS

Manual brake adjusters must be readjusted on a regular

basis. If your vehicle has manual brake adjusters, you can

readjust them if you’ve had the proper training.

READJUSTING AUTOMATIC 

BRAKE ADJUSTERS

Automatic brake adjusters normally don’t require manual

readjustment. If you have a brake that is over-stroking and

it has an automatic brake adjuster, you have a problem with

the brake or the adjuster. If you readjust it, you aren’t really

fixing the problem. The same is true if someone else only

readjusts it, the problem is still there.

A manual readjustment may bring the brake back into

compliance and improve the way the brake operates, but it

will only be temporary.

When you have automatic brake adjusters that are

over-stroking, there are some things you need to know

before you even think about readjusting them.

You may be legally prohibited from readjusting 

automatic brake adjusters in some jurisdictions.

Your employer may prohibit you from readjusting 

automatic brake adjusters.

You shouldn’t readjust an automatic brake adjuster 

unless you have been trained on exactly how to do it.

Readjusting an automatic brake adjuster improperly 

can damage it.

The brake will go out of adjustment again 

until the cause of the problem is repaired. It can go

out of adjustment very quickly.

If the brake is over-stroking, you need to check the 

free stroke or slack before you decide to readjust it.

If this distance is also longer than normal, a

readjustment may temporarily correct the problem.

You have to re-check the pushrod stroke and freestroke or slack after re-adjusting the brake. The

pushrod stroke must now be less than the adjustment

limit and the free stroke or slack must be in its normal

range. If either of these is not the case, do not

proceed. The brake is defective.

If you readjust the brake, you will have to take 

responsibility for doing so. This means you must

continue to monitor it and report the problem at the

first opportunity.

If you hire someone to correct an over-stroking 

problem on a brake with an automatic adjuster, be sure

they know what they are doing.

YOU MUST MEASURE 

THE STROKE TO CONFIRM 

THAT A BRAKE IS 

PROPERLY ADJUSTED.

FIGURES: The difference between the released and applied position

of the brake linkage must be less than the adjustment limit.

Brake Released

Measure stroke at “A” or “B”

with 90 to 100 psi in tank

and brakes fully applied

Appendix C 63 Highway Accident Report
Why It’s So 

Important To Keep Your Brakes 

Properly Adjusted

As a professional driver, you know there will be

times when you really need your brakes. Having

good brakes can get you out of a bad situation

when another driver makes a serious driving error

or some event requires extreme braking.

To be able to rely on your brakes in every driving

situation, they must be properly adjusted. When

your brakes aren’t properly adjusted, they will let

you down. Trucks that don’t stop the way they

should can put people’s lives at risk, including your

own.

Trucks and trailers that operate with brakes out of

adjustment are the most common reasons that drivers

and vehicle operators are charged with violations.

By taking the time to properly check brake

adjustment, you’ll make sure your vehicle is safe and

you’ll also avoid being charged with a violation.

Whenever checking the brake adjustment, always

be on the lookout for other defects like: damaged,

broken or missing components, rusty drums and

brakes that aren’t working.

Appendix C 64 Highway Accident Report
65 Highway Accident Report

Appendix D

Previous Safety Board Recommendations on Brake Adjustment 

and Inspection Issues

Brake Adjustment Guidelines. In 1975, the Safety Board investigated an 

accident involving a tractor-semitrailer that lost braking capability while descending a 

steep grade near Bishop, California.1 The vehicle began accelerating at a point 5 to 5 1/2 

miles from a truck parking area, where the driver had stopped to adjust the brakes. While 

the driver was attempting to negotiate a curve, the trailer separated from the tractor, 

overturned in front of a pickup truck and attached camper-trailer traveling in the opposite 

direction, and struck the other vehicle, causing it to burst into flames. All seven occupants 

were killed. As a result, the Safety Board recommended that the Federal Highway 

Administration (FHWA):

H-75-17

Develop and disseminate throughout the motor carrier industry, an “On 

Guard” bulletin alerting drivers of commercial vehicles equipped with 

externally adjustable braking systems of: a) the need to be familiar with 

company policies and practices with respect to on-road adjustment of 

brakes; b) methods and techniques for detecting potential or existing 

problems in adjustment; c) the scope of the problem in insuring proper 

brake adjustment; d) methods or techniques for the proper on-road 

adjustment of braking systems currently and generally in use.

In response, the FHWA developed a bulletin entitled Danger-Driver Adjusted 

Brakes, which was circulated to all carriers for display on bulletin boards and distribution 

to drivers and safety supervisors. The Safety Board classified this recommendation 

“Closed—Acceptable Action” on October 20, 1977.

A similar recommendation resulted from the Safety Board’s 1992 safety study on 

heavy vehicle air brake performance.2 The Safety Board recommended that the National 

Private Truck Council, the Owner-Operator Independent Driver Association, and the 

American Trucking Associations, Inc., (ATA) work with one another

1 National Transportation Safety Board, Francisco Flores Truck/Pickup Truck with Camper and 

Trailer Collision, U.S. Route 395, Bishop, California, June 29, 1974, Highway Accident Report 

NTSB/HAR-75/05 (Washington, DC: NTSB, 1975).

2 National Transportation Safety Board, Heavy Vehicle Airbrake Performance, Safety Study 

NTSB/SS-92/01 (Washington, DC: NTSB, 1992).
Appendix D 66 Highway Accident Report

H-92-67, -72, and -74

To complete and distribute to member carriers appropriate brake 

maintenance materials that clearly establish standard inspection techniques 

(including adjustment indicators), inspection and adjustment interval 

guidelines, and an adjustment method (covering both manual and 

automatic slack adjusters) for S-cam brakes on heavy vehicles. Encourage 

members to provide a copy of the information to each driver of a heavy 

vehicle and to each mechanic who services heavy vehicles.

On July 29, 2002, the Safety Board classified Safety Recommendation H-92-67 to 

the National Private Truck Council “Closed—Unacceptable Action/No Response 

Received.”

In 1993, the Owner-Operator Independent Driver Association produced and 

distributed more than 15,000 copies of a brake videotape and accompanying booklet, 

entitled What’s Stopping You?, which stressed the importance of regular preventive brake 

maintenance, provided an overview of roadside inspection procedures, and warned of the 

potentially serious consequences of mismatching brake components. Also included in the 

pamphlet was information from the FHWA and the University of Michigan Transportation 

Research Institute on downhill braking techniques. The Safety Board classified Safety 

Recommendation H-92-72 to the Owner-Operator Independent Driver Association 

“Closed—Acceptable Action” on January 30, 2001.

Through its maintenance council, the ATA developed a training video on how to 

conduct truck brake inspection and maintenance. In 1992, the ATA informed the Safety 

Board that efforts were under way with the FHWA’s Office of Motor Carriers to develop a 

method carriers could use to establish an appropriate brake adjustment interval for their 

own operations. The Federal Motor Carrier Safety Administration (FMCSA) Web site 

now contains a comprehensive list of brake maintenance materials and guidelines. The 

Safety Board classified Safety Recommendation H-92-74 to the ATA “Closed—

Acceptable Action” on July 16, 2002.

Automatic Slack Adjusters and Out-of-Adjustment Indicators. Beginning in 

1978, the Safety Board made several safety recommendations to require that vehicles be 

equipped with automatic slack adjusters and out-of-adjustment indicators.3 In 1977 and 

1978, the Safety Board investigated five accidents in which commercial vehicle drivers were 

unable to maintain speed control on downgrades. The major causal factor in four of these 

accidents was improper adjustment of the vehicles’ service brakes; in the fifth accident, the 

trailer brakes were totally inoperative. In two instances, the owners and operators had failed 

to ensure that the vehicles were safe for operation before they were dispatched.

In its 1992 study of heavy vehicle air brake performance,4 the Safety Board issued 

safety recommendations that superseded those resulting from the investigations conducted 

3 Safety Recommendations H-78-48 and H-88-30 were superseded by Safety Recommendation H-92-

50. Safety Recommendations H-81-1 and H-88-32 were superseded by Safety Recommendation H-92-51.

4 NTSB/SS-92/01.
Appendix D 67 Highway Accident Report

in the 1970s and 1980s. The Board cited numerous brake deficiencies, including serious 

instances of out-of-adjustment brakes, as causal or contributing factors in the accidents 

investigated to support the 1992 safety study. The Safety Board urged the National 

Highway Traffic Safety Administration (NHTSA) to

H-92-50

Require that air-braked vehicles be equipped with visible adjustment 

indicators that will allow one person to check the level of adjustment.

H-92-51

Expedite the proposed rulemaking to require automatic adjusters on 

vehicles equipped with air brake systems.

NHTSA issued a final rule on October 20, 1992, amending Federal Motor Vehicle 

Safety Standard 121, “Air Brake Systems,” and Federal Motor Vehicle Safety Standard 

105, “Hydraulic Brake Systems,” to require automatic brake adjusters on all air-braked 

and hydraulic-braked vehicles manufactured after October 20, 1994. Consequently, the 

Safety Board classified both recommendations “Closed—Acceptable Action” on 

December 21, 1992.

The Safety Board also recommended that the FHWA

H-92-57

Encourage the installation of vehicle brake adjustment indicators on all 

vehicles equipped with air brake systems for easy detection of adjustment 

levels.

In 1995, the FHWA published a report entitled Evaluation of Brake Adjustment 

Criteria for Heavy Trucks, which presented analyses, findings, and recommendations 

concerning the brake adjustment criteria of the North American Uniform Driver-Vehicle 

Inspection Criteria for Heavy Trucks. The FHWA also issued a final rule requiring motor 

carriers that have vehicles manufactured on or after October 20, 1994, to retain automatic 

brake adjustment indicators. The Safety Board classified this recommendation “Closed—

Acceptable Action” on February 5, 1996.

Brake Inspection. In 2002, the Safety Board issued an accident report on a 

May 31, 2001, accident that took place near Mountainburg, Arkansas, when a Gayle Stuart 

Trucking, Inc., truck-tractor semitrailer collided with a 65-passenger school bus operated 

by the Mountainburg, Arkansas, public schools. Three school bus passengers were fatally 

injured; two other passengers received serious injuries. Four passengers, the school bus 

driver, and the truck driver sustained minor injuries.5

5 National Transportation Safety Board, Collision Between Truck-Tractor Semitrailer and School Bus 

Near Mountainburg, Arkansas, May 31, 2001, Highway Accident Report NTSB/HAR-02/03 (Washington, 

DC: NTSB, 2002).
Appendix D 68 Highway Accident Report

One of the major safety issues discussed in the report was the poor condition of the 

tractor-semitrailer’s brakes. In the report, the Safety Board noted that the tractorsemitrailer was equipped with manual slack adjusters on the tractor brakes and automatic 

slack adjusters on the trailer brakes. Postaccident, 8 of the 10 brakes were found to have 

been either out of adjustment or nonfunctional at the time of the accident; at least 4 brakes 

could not have provided any braking force. The Safety Board concluded that six brakes on 

the tractor were out of adjustment either because the owner had not properly adjusted 

them, or because the brakes went out of adjustment due to a disproportional workload, or 

both.

The Mountainburg driver said he visually inspected the brakes on the day of the 

accident and did not find them to be out of adjustment. However, during the pretrip 

inspection, the driver did not follow the recommended practice of pulling on the 

pushrod and measuring the stroke to determine whether the brakes were out of 

adjustment. The Safety Board concluded that the driver did not conduct a sufficiently 

thorough pretrip inspection on either the tractor or the trailer to discover brake 

deficiencies. The regulation covering pretrip driver inspections, 49 Code of Federal 

Regulations (CFR) 396.13(a), stipulates only that the driver be satisfied that the motor 

vehicle is in safe operating condition before beginning driving; the regulation does not 

specify what must be done during a pretrip inspection or which procedures must be 

performed daily on the vehicle. The Safety Board issued the following safety 

recommendation to the FMCSA:

H-02-15

Revise 49 Code of Federal Regulations 396.13, Driver Inspection, to 

require minimum pretrip inspection procedures for determining brake 

adjustment.

In its initial response to this recommendation, dated January 3, 2003, the FMCSA 

stated that it considered that Federal regulations already adequately covered the intent of 

this recommendation, because (under 49 CFR 396.13(a)) the driver must be satisfied that 

the vehicle is in safe operating condition, including (under 49 CFR 392.71) that specified 

parts, such as the service brakes and the hand brake, are in good working order. Following 

this FMCSA response, the Safety Board classified the recommendation “Open—

Unacceptable Response” on July 1, 2003. The FMCSA sent another response, dated 

August 9, 2004, requesting reconsideration of this classification. On January 25, 2005, the 

Safety Board stated its classification of Safety Recommendation H-02-15 would remain 

“Open—Unacceptable Response.”

The Mountainburg accident investigation also raised issues concerning the 

qualifications of brake inspectors. Title 49 CFR 396.25, “Qualification of Brake 

Inspectors,” requires that each brake inspector successfully complete an apprenticeship or 

training program or have a certificate of experience totaling at least 1 year. The person 

responsible for maintaining the brakes on the trailer of the Mountainburg accident vehicle 

could prove the required experience; however, he failed to notice problems that a qualified 
Appendix D 69 Highway Accident Report

mechanic should have noticed during routine maintenance and inspections. The Safety 

Board concluded that the carrier’s mechanic lacked proper training in brake maintenance 

and inspections, did not detect the poorly adjusted or inoperative brakes on the trailer, and 

did not perform recommended maintenance. Under the FMCSA’s motor carrier 

compliance review process, a violation of 49 CFR 396.25 is not considered “Critical.” 

Thus, if a carrier does not have a qualified brake inspector, its rating is not affected. 

Consequently, the Safety Board issued the following safety recommendation to the 

FMCSA:

H-02-17

During compliance reviews, rate companies as unsatisfactory in the vehicle 

factor category if the mechanics and drivers responsible for maintaining 

brake systems are not qualified brake inspectors.

In its initial response to Safety Recommendation H-02-17, dated January 3, 2003, 

the FMCSA stated that it would review its process of assessing motor carriers’ safety 

management control activities that influence the vehicle factor of a carrier’s safety rating. 

The Safety Board classified the recommendation “Open—Acceptable Response” on 

July 1, 2003. In a May 28, 2004, letter to the Safety Board concerning this 

recommendation, the FMCSA stated

Because our safety fitness rating methodology is based on the overall performance 

(e.g., vehicle, driver, accident) of a motor carrier during a compliance review, we 

do not take the specific approach recommended by NTSB. We are concerned that 

basing the rating on only one single component of the carrier’s operation—the 

vehicle portion—would not yield a fair determination of the carrier’s overall 

safety fitness, and hence, would not result in increased effectiveness. FMCSA’s 

investigators do review carrier profiles prior to each and every compliance review. 

As a matter of standard practice, if the profile indicates evidence of brake 

problems, the investigator focuses his or her investigation on the inspection and 

maintenance of the vehicles, including the qualifications of brake inspectors.

In its December 15, 2004, response to the FMCSA, the Safety Board indicated that 

the Board continues to believe that implementation of Safety Recommendation H-02-17 is 

necessary, given that brake failures have dire consequences for traffic safety. The Board 

noted that it was aware the FMCSA had published an advance notice of proposed 

rulemaking in 1998 that was intended to lead to a more performance-based rating system. 

The Board also stated that it understood from previous correspondence that the FMCSA 

would factor the recommendation into its plans as it proceeds to issuing a notice of 

proposed rulemaking (NPRM). The Board noted that it would consider the FMCSA’s 

response acceptable if the NPRM and final rule address brake mechanic qualifications. 

Pending such action, the Safety Board classified Safety Recommendation H-02-17 

“Open—Unacceptable Response.”
Appendix D 70 Highway Accident Report

Also in the Mountainburg report, to ensure that mechanics working on truck brake 

systems for carriers have the knowledge necessary to maintain such systems, the Safety 

Board issued the following safety recommendation to the FMCSA:

H-02-18

Revise 49 Code of Federal Regulations 396.25, Qualifications of Brake 

Inspectors, to require certification after testing as a prerequisite for 

qualification and specify, at a minimum, formal training in brake 

maintenance and inspection.

In its initial (January 3, 2003) response to Safety Recommendation H-02-18, the 

FMSCA stated that it would research the training, examination, and certification 

requirements of organizations that certify automotive mechanics and then evaluate the 

results of the research and determine the appropriate next steps. On July 1, 2003, the 

Safety Board classified this recommendation “Open—Acceptable Response.” 

Subsequently, in a letter dated August 9, 2004, the FMCSA indicated that implementing 

Safety Recommendation H-02-18 would impose a significantly increased burden on 

motor carriers and suggested alternative approaches to fulfilling the intent of the 

recommendation. The Safety Board did not find the alternatives satisfactory and 

reclassified the recommendation “Open—Unacceptable Response” on January 25, 2005.