PB98-916201

NTSB/HAR-98/0l/SUM

NATIONAL

TRANSPORTATION

SAFETY

BOARD

WASHINGTON, D.C. 20594

HIGHWAY ACCIDENT SUMMARY

REPORT

BUS COLLISION WITH PEDESTRIANS

NORMANDY, MISSOURI

JUNE 11, 1997

6949A

L / U S GOVERNMENTT PRINTING OFFICE 1989 0-942-865
Abstract: On June 11, 1997, a transit bus collided with seven pedestrians at a “park and ride” transit

facility in Normandy, Missouri. The bus was being operated by a driver trainee who had just completed a

routine stop at the station. After allowing the passengers to debark from the bus, the driver trainee began

to move the bus forward to provide clearance for another bus to pass. The driver trainee, who was

reportedly unable to stop the bus, allowed it to surmount the curb and continue onto the station platform.

The resulting encroachment onto the platform resulted in the deaths of four pedestrians and injuries to

three others.

The safety issues discussed in this report are the sufficiency of pedestrian protection provided by

the saw-tooth parking bay design and the need for positive separation between the roadway and

pedestrian areas of parking bay facilities.

As a result of its investigation, the National Transportation Safety Board issued recommendations

to the Federal Highway Administration, the Federal Transit Administration, the American Association of

State Highway and Transportation Officials, the American Public Transit Association, and the

Community Transportation Association of America.

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.

Information about available publications may be obtained by contacting:

National Transportation Safety Board

Public Inquiries Section, RE-51

490 L’Enfant Plaza, S.W.

Washington, D.C. 20594

(202) 314-6551

Safety Board publications may be purchased, by individual copy or by subscription, from:

National Technical Information Service

5285 Port Royal Road

Springfield, Virginia 22161

(703) 605-6000
$75 %1..+5+10 9+6* 2'&'564+#05

014/#0&;."/+55174+

,70'"33."3;;9

HIGHWAY ACCIDENT SUMMARY REPORT

Adopted: February 19, 1998

Notation 6949A

0#6+10#.

64#052146#6+10

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HIGHWAY ACCIDENT SUMMARY

Accident No.: CRH-97-F-H007

Vehicle: 1981 GMC T8H-5307A transit bus

Accident Type: Collision with pedestrians

Location: Normandy, Missouri

Date: June 11, 1997

Time: 9:15 a.m.

Owner/Operator: Bi-State Development Agency

Occupants: Driver trainee and line instructor

Damage: Minor damage to bus and facility structures

Injuries: Four pedestrian fatalities; two serious and one minor pedestrian injuries

About 9:15 a.m.1

 on June 11, 1997, a 1981

General Motors Corporation (GMC) transit bus

collided with seven pedestrians at a “park and

ride” transit facility in Normandy, Missouri. The

bus was being operated by a driver trainee who

had just completed a routine stop at the station.

After allowing the passengers to debark from

the bus, the driver trainee began to move the bus

forward to provide clearance for another bus to

pass. The driver trainee, who was reportedly

unable to stop the bus, allowed it to surmount

the curb and continue onto the station platform.

The resulting encroachment onto the platform

(see figure 1) resulted in the deaths of four

pedestrians and injuries to three others.

 

1

All times are given in central daylight time.

During its investigation, the National

Transportation Safety Board identified two

safety issues: the sufficiency of pedestrian

protection provided by the saw-tooth parking

bay design and the need for positive separation

between the roadway and pedestrian areas of

parking bay facilities. The following discussion

includes a narrative description of the accident;

an overview of the causal issues explored

relating to the vehicle’s operational characteristics, equipment design, and operator

conditions and actions; a detailed examination

of the safety issues; and a list of conclusions and

safety recommendations developed to help

prevent future accidents of this type.

National Transportation Safety Board

Washington, D.C. 20594
2

Preaccident Events

On June 11, 1997, at 4:25 a.m., a driver

trainee, along with her instructor, departed from

the Bi-State Development Agency (BSDA)

Debaliviere facility in St. Louis, Missouri. The

trainee was completing her final week of a 6-

week training program and was scheduled to fill

a position as a part-time busdriver at the end of

the week. Initially that day, the driver trainee

was on the bus as an observer while the

instructor drove their route. At some time

between 6:30 and 7 a.m., the driver trainee

switched places with the instructor and took

over as the bus’s operator. The weather that

morning was partly cloudy but dry, with

temperatures around 70°F. At 9 a.m., the bus

made a scheduled stop at the University of

Missouri at St. Louis-South MetroLink facility

in Normandy, Missouri. The driver trainee

pulled around and parked in front of another bus

that was already parked at the location. (See

figures 1, 2, and 3.)

The Accident

After the bus passengers debarked from the

vehicle, the driver trainee and her instructor

prepared to exit the bus for a short break. As

they were doing so, the operator of the bus

parked behind the accident vehicle signaled for

them to pull forward to provide him with

sufficient passing clearance.

The instructor, who was standing within the

accident bus by the front exit door, told the

driver trainee to pull the bus forward. The

trainee reported that she then performed the

following actions:

Figure 1 -- Diagram of accident scene

INVESTIGATION AND ANALYSIS

Accident Vehicle

Retaining Wall

Not

Mapped

Not

Mapped

0 5' 10' 20' 40'

North

Rail Station Platform

Previously Parked Bus

Pedestrian Platform

Retaining Wall

Wall - Stairs

Not

Mapped

Path traveled by

Accident Vehicle

Pedestrian Shelters

Loose Dirt

Long Term

Parking Area

Loose Dirt

Not

Mapped
3

Figure 2 -- View from roadway toward pedestrian shelters

Figure 3 -- Bus parked in space used by the accident vehicle
4

• Placed her foot on the brake pedal,

• Moved the transmission gear

selector into the drive position,

• Closed the doors,

• Released the emergency brake, and

• Slowly released pressure from the

brake pedal.

The bus moved forward approximately 14

feet before surmounting the 5-inch-high curb

dividing the roadway from the pedestrian

platform. The bus continued forward onto the

platform for a distance of 25 feet before making

contact with the first of two pedestrian shelters.

Then, after striking the second shelter and

traveling an additional 93 feet, the bus came to a

halt against a section of metal railing. (See

figure 4.) The resulting encroachment onto the

platform and collision with two pedestrian

shelters resulted in the death of four pedestrians

and injury to three others.

The driver’s instructor later told

investigators that at some point during the bus’s

forward progress, he activated the emergency

stop switch on the bus. The switch had been

designed to close down all functions on a

runaway engine by depriving it of air.

Figure 4 -- Bus collision movements

Pedestrian Shelters

Area Not

Mapped

93'

1 32' Pedestrian Platform

40'

Retaining Wall

0 5' 20' 10'

25'

14'

Area Not

Mapped

Area Not

Mapped

Metal

Railing
5

The driver trainee and the line instructor

were transported to Normandy Community

Hospital, where both provided blood and urine

specimens for analysis. The toxicological test

results were negative for alcohol and other

specified drugs.2

 Subsequently, the Safety Board

obtained a sample of these specimens and sent

them to the Center for Human Toxicology

(CHT) in Salt Lake City, Utah, for analysis. The

results of the CHT tests were negative for drugs

and alcohol.

The three injured pedestrians were also

taken to the Normandy Community Hospital for

treatment. The four deceased pedestrians were

transported to the Depaul Health Center in St.

Louis.

Postaccident Events

The bus was towed from the accident scene

to the BSDA’s principal maintenance facility,

located at 3333 Spruce Street, in St. Louis,

Missouri, where Safety Board investigators and

officers from the Missouri State Highway Patrol

Commercial Vehicle Enforcement Section

inspected the vehicle. The inspections revealed

that the vehicle’s brakes were all adjusted

within specifications. No defective items

relating to the collision were observed.

Investigators found the emergency stop switch

in the activated position. They further found that

the switch had been disconnected.

This accident resulted from the unintended

forward progress into the pedestrian area of the

bus driven by the trainee. In its investigation,

the Safety Board attempted to determine what

caused this movement by reviewing: the

condition of the bus and its equipment; the

design of the bus pedals; and the training,

experience, and condition of the driver.

Bus Information

General -- The 40-foot transit vehicle was a

1981 GMC bus that had been purchased new by

the BSDA. Maintenance on the vehicle had been

performed at BSDA facilities since the

purchase. The vehicle had last undergone a

 

2

Cocaine, amphetamines, marijuana, PCP, and

opiates.

routine 3,000-mile safety inspection on June 10,

1997, the day before the accident.

The bus was equipped with a rear-mounted,

Detroit Diesel 8V713

 engine. The engine’s fuel

system components included a mechanical geardriven supercharger and a mechanical fuel

injection system. Throttle position was regulated

by a foot-activated treadle valve using air

pressure to control the throttle assembly.

Additionally, separate throttle position controls

regulated “fast idle” activation and setting. A

solenoid was used for emergency engine

shutdown.

Brake System -- The brake system included

a service brake, an air/mechanical parking

brake, and a solenoid-activated air brake system

incorporated into the operation of the rear

passenger loading doors. The air brake system

complied with 49 Code of Federal Regulations,

Section 571.121, Standard No. 121; Air brake

systems.4

 All brakes were equipped with Haldex

automatic slack adjusters.

Examination of the brake system revealed

the following:

• Service brake application was

controlled by a foot-activated

treadle valve. Operation of the valve

supplied air pressure to both front

and rear axle service brake

chambers.

• Parking brake activation was

controlled by a floorboard-mounted

hand valve located to the left of the

driver’s seat. Operation of the valve

regulated air into the parking/emergency brake chambers on the rear

axle. Air pressure to the brake

chambers was restricted to between

60 and 80 psi. Activation of this

valve also bled air from the roller

lock plunger assembly, causing the

rear brake pushrods to be

 

3

The “8” indicates the total number of cylinders and

the “71” denotes cubic inches per cylinder, equating to a

total displacement of 568 cubic inches.

4

This standard establishes performance and equipment

requirements for braking systems on vehicles equipped

with air brake systems.
6

mechanically locked in the

“applied” position.

• Release of the parking brake

required two separate actions. First,

the hand valve had to be pushed

inward. This action bled air pressure

from the parking brake chamber and

allowed air pressure back into the

roller lock plunger assembly. Even

though air pressure was reapplied to

the roller lock plunger assembly, the

level of pressure was insufficient to

overcome the mechanical force

acting on the brake pushrod. The

second required action was the

application of the service brake.

This allowed air pressure into the

service brake chamber, which in

turn moved the brake pushrod

forward. This forward movement

disengaged the mechanical lock of

the roller lock assembly. Only after

the service brake had been disengaged were the brakes completely

released.

• The rear door interlock, which was

controlled by a lever at the left side

of the driver’s control panel,

activated an electronic locking

mechanism on the rear passenger

loading door, disabled the accelerator, and allowed air pressure into

the rear axle service brakes. When

the lever was rotated, an electronic

solenoid retracted the door’s

locking lever. Once unlocked, the

door could be manually opened. At

the same time, the throttle was

deactivated so that when the

accelerator was depressed no movement was transmitted to the

engine’s throttle assembly. In

addition, air pressure, limited to 40

psi, was supplied to the rear axle

service brake chambers. The system

was designed so that the rear brakes

would have sufficient force to hold

the vehicle while passengers exited.

It was not designed to function as a

separate brake system to slow or

stop the bus.

Emergency Stop Switch -- The line

instructor told investigators that during the

accident he had activated the emergency stop

switch in the bus. This switch was designed, in

the event of a runaway engine, to stop all engine

functions by depriving the engine of air. After

the accident, investigators found this switch in

the activated position. Further inspection

revealed that the emergency stop switch had

been disconnected, so the activation of the

switch had no effect on the bus’s operation.

BSDA representatives told investigators that

the bus’s fuel injection system had previously

been modified so that the possibility of a

runaway engine condition due to a stuck injector

had been eliminated. Consequently, the switch

had been disconnected. Investigators attempted

to determine whether activation of the shutoff

function could have had any effect on this

accident.

The engine’s mechanical fuel injection

system, as originally manufactured, was

equipped with “non-spring-loaded” injector

control tube assemblies. The assembly was

designed such that, under certain circumstances,5

 a runaway engine condition could

occur. Because of the possibility of runaway, the

engine’s air inlet housing was equipped with an

emergency air shutoff valve. The valve was

controlled by an electrical switch mounted on

the left side of the vehicle’s dashboard.

Activation of the switch caused the valve to

close, preventing air from entering the engine,

thus shutting down a runaway engine.

 

5

The control tubes were mounted along the top of each

cylinder head and supported on each end by a bracket

assembly that allowed the tubes to rotate. A series of rack

levers, one for each cylinder, was affixed to each control

tube. The opposing end of each rack lever was connected to

a fuel metering rod, which fit inside a fuel injector housing.

The assembly was designed so that throttle activation

caused each control tube to rotate in a direction opposite

from the fuel injector housing. The rack lever converted the

rotational movement of the control tube into a linear

motion acting on the fuel metering rod. As the control tube

rotated away from the fuel injector housing, the rack lever

slid the fuel metering rod out, allowing more fuel to enter

the injector housing. The rack levers were mounted to the

control tubes by two opposing adjustment screws with lock

nuts. Because of this, if one fuel metering rod were to stay

in a full fuel position, the remaining rods would also be in

full fuel delivery, thereby causing a runaway engine

condition.
7

Further investigation, however, revealed

that engine shutdown upon activation of the

switch was not immediate and would only occur

after the oxygen supply to the engine had been

sufficiently depleted. Even if the fuel injection

system had remained as originally designed and

the emergency stop switch had been connected

to the air shutoff valve, the shutdown feature

would have taken too long to have had any

effect on the outcome of this accident.

Therefore, the Safety Board concludes that

activation of the emergency stop switch could

not have averted this accident.

Pedal Configuration -- Physical

examination of the throttle/brake pedal assembly

revealed that the pedals were similar in design

and surface texture. The accelerator pedal was

approximately 11 3/8 inches long by 3 inches

wide. The brake pedal was approximately 12

inches long by 3 1/8 inches wide. The spacing

between the bases of the pedals was 1 3/4

inches, while the tops of the pedals were

separated by 1 inch. The brake pedal was

mounted so that it angled back, toward the fire

wall, at 47°. The accelerator was mounted in a

similar manner, except that it had a steeper 54°

angle. The accelerator facing was of textured

rubber with longitudinal grooves extending from

top to bottom. The lower portion of the brake

pedal was exposed metal; the upper portion was

covered by a grooved rubber insert. (See figure

5.)

Figure 5 -- Pedal configuration

Brake Pedal

Metal Surface

Metal Band

Textured

Rubber

Surface

Metal Plate

Textured 

Rubber

Surface

Accelerator Pedal
8

Experienced bus operators from the BSDA

Debaliviere facility were interviewed regarding

the vehicle’s pedal design and layout. Their

general belief about the pedals was that, because

of their similarity and close proximity, the

pedals’ configuration might appear

ergonomically awkward, especially to an

inexperienced operator such as the driver

trainee. They considered, however, that once an

individual had been trained, the arrangement of

the pedals represented no hindrance to proper

bus operation. Their experience-based opinions

are supported by past research that found no

systematic link between unintended acceleration

due to misapplication of pedals and pedal

design.6

Operator Information

Driver Trainee -- The 31-year-old driver

trainee had been employed by the BSDA since

May 5, 1997. Although the trainee had held an

operator’s license since she was a teenager, she

had no prior experience as a professional driver

nor any history of heavy vehicle operations. An

inquiry with the National Drivers Register data

base and a State driver’s license check disclosed

only one violation pertaining to the trainee, a

1994 speeding citation. Her work/rest cycle was

examined for the 96-hour period preceding the

accident, and no evidence of fatigue was found.

The trainee possessed a valid medical certificate

and a Missouri commercial driver’s license

(CDL) that certified her to operate the accident

vehicle. She had obtained her CDL on June 4,

1997, based on training she had received from

the BSDA, and was in the final week of the

BSDA’s 6-week bus operator training program.

Based on the available information

regarding the trainee’s condition, the Safety

Board concludes that the driver trainee was not

fatigued, impaired, or suffering from any

medical conditions that may have affected her

performance.

Motor Carrier -- The BSDA is a quasipublic,7

 not-for-profit agency that operates

 

6

Schmidt, Richard A., 1989, Unintended

Acceleration: A Review of Human Factors Contributions.

The Human Factors Society.

7

The BSDA has no taxing power but is authorized to

issue revenue bonds, collect fees, and receive funds from

public transportation services within the St.

Louis, Missouri, and East St. Louis, Illinois,

region—an area covering 3,600 square miles

and 200 municipalities. The BSDA can cross

local and State boundaries, as provided through

a 1949 compact between Missouri and Illinois

that was ratified by the U.S. Congress. In 1963,

the BSDA purchased and consolidated the

area’s 15 privately owned transit firms.

The BSDA operates 600 transit buses, with

an average fleet age of 8 years. The BSDA

transit system typically operates from 4:30 a.m.

to 1 a.m. the following day. Bus service

encompasses 116 scheduled routes, consisting

of 18,500 bus stops and 640 bus shelters. During

periods of peak service, an average of 507 buses

are in operation. During FY8

 1996, the bus fleet

traveled 23 million miles, for an average of

80,140 miles per day, and was involved in a

total of 529 Federal Transit Administration

(FTA)-reportable collisions.9

 In FY 1997,

BSDA buses were involved in 404 FTAreportable collisions.

At the time of the Normandy accident, the

BSDA employed about 1,950 people, of which

850 were full-time and 109 were part-time

drivers. The BSDA initially hires drivers on a

part-time basis and then promotes them to fulltime status as positions become available.

Drivers generally select routes and schedules

periodically, based on their seniority. On their

days off or during hours they are not driving,

drivers can report to the station and try to pick

up extra routes that may be available.

The BSDA provides 6 weeks of training to

newly recruited drivers before they are allowed

to operate a vehicle without supervision. The

first week of the bus operator training program

covers bus orientation and is conducted in a

classroom environment. The second week of

training includes additional classroom

instruction and exposes the student to actual bus

operations in a controlled environment. Later in

that week, the student is allowed to operate a

 

Federal, State, local, and private agencies.

8

The BSDA’s fiscal year runs from July 1 through

June 30.

9

The FTA requires the reporting of any collision

involving death or injury or damage exceeding $1,000.
9

bus on a public road but is not engaged in

passenger service. The remaining 4 weeks of

training are devoted to actual passenger service

over established routes; however, the student is

still under the supervision of an on-board

instructor.

Bus System Performance Tests

Test Drive -- The accident bus’s brake

system was visually examined and

measurements of the brake system adjustment

were obtained. No defects were noted, and a test

drive was performed with BSDA personnel

operating the vehicle. During the test drive,

multiple stops were made at various speeds10

and the dynamic brake performance was found

to be satisfactory throughout the testing period.

The steering system was also evaluated during

the test drive. When the bus was maneuvered

both left and right, no unusual feedback in the

steering system was observed, and the vehicle

followed a normal track.

The accident bus’s "steering wheel lash"

was measured at the conclusion of the test drive

and found to be 5 1/2 inches. Steering wheel

lash is the distance the steering wheel will turn

before initiating any detectable movement by

the front wheels. The Commercial Vehicle

Safety Alliance out-of-service criteria dictate

that a vehicle equipped with a manual steering

system controlled by a 21-inch steering wheel

would be in an out-of-service condition if

steering wheel lash were measured at 5 1/2

inches or more.

Engine Performance and Throttle

Activation -- Investigators also examined engine

performance and throttle activation. Using the

accelerator pedal, engine revolutions per minute

(rpm) were brought to various levels. The

throttle was then released and the engine

returned to a normal idle speed during each test.

Engine performance was also monitored during

the test drive. No defects were noted.

Acceleration tests were conducted using two

different procedures. All tests were performed

on a level surface with the bus starting from a

 

10Actual speeds could not be determined, as the

accident vehicle’s speedometer was inoperative.

complete stop; the bus was then timed as it

accelerated over a distance of 150 feet. The test

conditions did not include provision of a 5-inch

curb, such as that in place at the accident

location, because investigators determined that

the curb did not provide enough obstructive

force to affect the acceleration of the vehicle in

any significant way. The height of the curb

relative to the circumference of each bus tire

(21-inch rolling radius), the fact that each tire

surmounted the curb independently, and the

steep (55°) angle of approach taken by each tire

(see figure 6) indicated that the 5-inch curb was

not a meaningful barrier to the bus.

Figure 6 -- Curb and tire profiles

During the first set of tests, the service

brakes were applied, the engine was at normal

idle speed, the transmission was placed in drive,

the service brake was released, and full throttle

was applied. Wide open throttle was maintained

while the bus accelerated over the test distance.

(See table 1 for test results.)

The second set of tests involved bringing

the engine rpm up to a range of approximately

1,200 to 1,500 rpm.11 The transmission was in

neutral, and no brakes were applied. The

transmission was then shifted into drive and the

accelerator was simultaneously depressed, so

that full throttle was applied. Wide open throttle

was maintained while the bus accelerated over

the test distance. (See table 2 for test results.)

 

11Engine rpm had to be estimated based on operator

experience, as the vehicle was not equipped with a

tachometer.

Road Surface

Tire Profile

showing 21-inch

rolling radius

5 "

Top View

showing tire contact 

with curb

Road Surface

Curb

Side View

showing tire contact 

with curb

55.0°

Curb
10

The engine is equipped with a manually

activated fast idle circuit controlled by an

electrical switch on the bus’s left side dash

panel. Fast idle operation can be initiated any

time that the switch is placed in the “on”

position; it operates independently of engine

temperature. The fast idle system is also

equipped with a drive gear interlock feature,

which is designed to reduce engine idle back to

normal rpm when the transmission is shifted

into drive while the fast idle is engaged.

To test the drive gear interlock, the engine

was allowed to warm up to normal operating

temperature with the transmission in neutral and

the parking brakes applied. The fast idle

activation switch was then placed in the “on”

position and an audible increase in engine rpm

was noted. The service brake was then applied

and the transmission was shifted into drive.

Immediately after the transmission was shifted

into drive, an audible decrease in engine rpm

was observed. These test procedures were

conducted two more times with the same results.

Brake Power Tests -- To determine

whether engine horsepower could overcome

brake application, a series of static brake tests

were performed to evaluate the effectiveness of

the accident vehicle’s braking system. The first

test involved the bus’s service brakes. During

this test, the bus was parked on a level surface

inside the BSDA’s primary maintenance facility.

The engine was allowed to warm up to a normal

operating temperature while the transmission

was in neutral and the parking brake was

applied. Once this temperature was attained, the

service brakes were applied and the parking

brake was released. With the service brakes still

applied, the accelerator was depressed to full

throttle. The engine was then held in a condition

of wide open throttle for about 30 seconds with

the service brakes applied. The service brakes

did not allow the vehicle to move during the

test.

The second test involved the parking brake.

To perform this test, the parking brake was

applied and the accelerator was depressed to full

throttle. The engine was then held in a condition

of wide open throttle for about 30 seconds with

Table 1* -- First series of acceleration tests

TEST

NUMBER

DISTANCE TRAVELED

IN FEET

TIME REQUIRED

IN SECONDS

ACCELERATION

FACTOR (g)

1 150 8.23 0.137

2 150 8.63 0.125

3 150 8.35 0.133

*Average time to travel 150 feet was found to be 8.40 seconds, with an average acceleration factor of 4.18 feet per

second per second.

Table 2* -- Second series of acceleration tests

TEST

NUMBER

DISTANCE TRAVELED

IN FEET

TIME REQUIRED

IN SECONDS

ACCELERATION

FACTOR (g)

4 150 7.50 0.165

5 150 7.64 0.159

6 150 7.38 0.171

*Average time to travel 150 feet was found to be 7.50 seconds, with an average acceleration factor of 5.15 feet per

second per second.
11

the parking brake applied. The parking brake

held the bus stationary throughout this test.

The third test also involved the parking

brake. During this test, the parking brake was

partially released. To perform this test, the

parking brake was applied and then released.

However, the service brakes were not applied

once the parking brake had been released.

Because of the design of the parking brake

system, the rear brake pushrods were still

mechanically locked in an “activated” position.

The bus remained stationary until the

accelerator was depressed to full throttle. With

the application of full throttle, the bus slowly

moved forward.

The final test involved the rear door

interlock system. During this test, both the

parking brakes and service brakes remained

unused. The rear door interlock lever was

engaged and the bus’s transmission was shifted

into drive. The bus remained stationary, and no

vehicle movement was observed. The

accelerator was depressed to full throttle, and no

increase in engine rpm was detected with the

engine remaining at idle speed.

In her statements to investigators, the driver

trainee maintained that she had applied the

brake throughout the accident sequence. The

investigation did not find any corroborative

evidence to verify the driver trainee’s assertion.

Analysis of the results from all the foregoing

tests demonstrated that the bus’s brake system

was adequate to hold the vehicle stationary

regardless of throttle position. Had the driver

trainee placed her foot on the service brake, as

she indicated to investigators, the bus would not

have accelerated forward, over-ridden the curb,

and traveled onto the pedestrian platform.

Additionally, had the driver trainee

inadvertently placed her foot on the accelerator

and then either removed it from the accelerator

and applied the service brake or applied the

service brake while the accelerator was still

depressed to wide open throttle, the bus would

have stopped. The Safety Board therefore

concludes that the driver trainee misapplied her

foot to the accelerator pedal, thereby causing the

unintended acceleration of the bus.

Time and Distance Calculations

Calculations, based on the bus’s lowest

tested rate of acceleration (4.18 feet per second

per second), indicate that from the moment it

first started moving the bus would have required

2.5 seconds to travel to the point where the right

front tire contacted the curb and would have

attained a speed of 7 mph. From there, it would

have taken an additional 1.8 seconds until the

front of the bus collided with the first pedestrian

shelter at a speed of 12 mph. Using the high

value attained during the acceleration tests (5.15

feet per second per second), the results would

have changed as follows: the bus would have

traveled the initial distance of 14 feet in 2.3

seconds and would have rolled over the curb at a

speed of 8 mph; then, continuing from the curb

to the collision with the pedestrian shelter would

have required an additional 1.6 seconds and the

bus would have been traveling at 13 mph at the

time of impact with the shelter. (See figure 7.)

The misapplication of the accelerator

resulted from the associated effect of numerous

conditions, including the inexperience of the

driver trainee, the close proximity of the pedals,

and the pedals’ similarity in shape and feel.

Under the influence of these conditions, the

driver trainee believed, as is common during

incidents of unintended acceleration,12 that she

was applying pressure to the brake pedal.

Because of this misapprehension, she

maintained a continuous application of the

accelerator until some point after the bus

collided with the pedestrian shelters. The Safety

Board therefore concludes that a combination of

factors contributed to the driver trainee’s pedal

misapplication. In light of the driver trainee’s

failure to recognize her mistake about the pedal

application, the relatively short distance traveled

by the accident vehicle before striking

pedestrians, and the limited time available under

the acceleration scenarios tested, the Safety

Board concludes that, once the bus began to

accelerate, the driver trainee did not have

sufficient time to avoid the encroachment onto

the pedestrian platform.

 

12Schmidt, Unintended Acceleration: A Review of

Human Factors Contributions.
12

Figure 7 -- Acceleration test scenarios

Accident Events

Based on low value

from Acceleration Tests

Accident Events

Based on high value

from Acceleration Tests

20'

Bus moves from "Parked

Position" and right front

tire contacts curb

Distance 14 Feet

Speed 8 MPH

Time 2.3 Sec.





Bus rolls over 5" curb

and continues forward

to collide with Shelter

Distance 39 Feet

Speed 13 MPH

Time 3.9 Sec.

14 FEET

2.3 SEC

25 FEET

1.6 SEC

Bus moves from "Parked

Position" and right front

tire contacts curb

Distance 14 Feet

Speed 7 MPH

Time 2.5 Sec.







25 FEET

1.8 SEC

14 FEET

2.5 SEC

Bus rolls over 5" curb

and continues forward

to collide with Shelter

Distance 39 Feet

Speed 12 MPH

Time 4.3 Sec.

0 5' 10'

Bus Continues forward

colliding with other

objects until coming 

to rest against railing

Distance 132 Feet

93 FEET

Bus Continues forward

colliding with other

objects until coming 

to rest against railing

Distance 132 Feet

40'

93 FEET
13

Given the rapidity with which the accident

developed, and the fact that the driver trainee

did not immediately recognize her error, she did

not have time to use steering input to avoid the

pedestrians. Investigators determined that once

the bus had surmounted the curb, the driver

trainee did not have sufficient time to steer the

bus to successfully avoid the collision with the

first pedestrian shelter. Consequently, the Safety

Board concludes that the excessive steering

wheel lash of the accident bus did not contribute

to the accident.
14

While investigating this accident, the Safety

Board found that the accident’s most significant

element was not its cause but its severity. In

many instances, a similar momentary error on

the part of a busdriver might have had far less

serious consequences — such as damage to the

bus and other property, slight injuries, or both.

In this case, however, four people died and two

suffered serious injuries. The crucial variable

was the presence of unprotected pedestrians in

the bus’s path. Therefore, the Safety Board

considered whether and how the effects of the

accident could have been mitigated. The safety

issues identified during the investigation were:

1. The sufficiency of pedestrian protection provided by the saw-tooth

parking bay design, and

2. The need for positive separation

between the roadway and pedestrian

areas of parking bay facilities.

Transit Station Facility Design

The BSDA’s MetroLink line has a total of

18 stations, 4 of which are designed with sawtooth bus parking bays similar to the accident

location. A review of the BSDA’s facility

design requirements revealed that, during design

development, attention was focused on avoiding

conflicts and crossovers between buses and

other vehicular traffic, as well as between buses

and pedestrian traffic. The BSDA design

specifications provided for, among other things,

“standard saw-tooth bus bay” parking spaces

and walkways to be paved and raised about 6

inches above the adjacent road surface.

No provisions were made for the

construction of barricades or other devices to

prevent vehicular traffic from entering areas of

pedestrian congregation. The only barrier

planned to be between the bus parking spaces

and the pedestrian platforms was a raised 6-

inch-high13 concrete curb. As a consequence of

 

13The measured height of the curb overrun by the

accident bus was 5 inches.

these design requirements and specifications,

the facilities incorporating the saw-tooth parking

bays were laid out in such a way that when

buses pull into the parking spaces, their forward

motion is directed toward areas where

pedestrians tend to congregate.

According to the BSDA’s deputy executive

director and general manager of engineering and

facilities management, the facility where the

accident occurred was designed and built in

accordance with guidelines common to the

transit industry. The saw-tooth design is

intended to facilitate station access by the

passenger buses and minimize interference from

pedestrian traffic. In 1981, the Urban Mass

Transportation Administration (UMTA)14

publicized the design specifications for sawtooth parking bays and illustrated their

efficiency in providing parking for multiple

buses. Additionally, the American Association

of State Highway and Transportation Officials

(AASHTO) guideline for park and ride

facilities15 states:

...where more than two buses are

expected to be using a facility at one

time, the saw-tooth arrangement is

generally preferable, because it is easier

for buses to bypass a waiting bus.

Although officials at neither the FTA nor

the American Public Transit Association

(APTA) could estimate the percentage of

stations using the saw-tooth configuration, the

Safety Board is aware that station designs

similar to the accident location have been used

nationwide for many years. A consulting

engineer employed by the BSDA told

investigators that the design has been commonly

used throughout his 40-year career.

While the Safety Board recognizes the

efficiency of the saw-tooth station design for

 

14In 1991, UMTA was reorganized into the FTA.

15AASHTO, A Policy on Geometric Design of

Highways and Streets,1994 edition.

SAFETY ISSUES
15

multiple bus parking, it is concerned that neither

the design specifications followed by the BSDA

nor the guidelines provided by UMTA or

AASHTO include any type of positive

separation that could prevent a defective or

poorly driven bus from encroaching onto the

pedestrian platform in normal (low-speed)

operating conditions for parking lot facilities. A

further selection from the AASHTO guideline

for park and ride facilities states that:

...the area delineating the passenger

refuge area should be curbed in order to

reduce the height between the ground

and the first bus step and reduce

encroachment by buses on the passenger

areas.

The Normandy station was designed in

accordance with this guideline, which calls for a

curb as the only separating device. The Safety

Board considers that design guidelines should

specify a positive separation barrier between the

bus parking bay and the pedestrian platform

sufficient to stop a bus operating under normal

parking area speed conditions from progressing

into the pedestrian area. The circumstances of

the Normandy accident clearly illustrate that the

curb-only separation cannot contain the forward

movement of a large bus. Consequently, the

Safety Board concludes that the current design

guidelines for saw-tooth parking bay configurations commonly followed by the transit

industry fail to provide adequate pedestrian

safety.

Therefore, the Safety Board believes that, in

cooperation, the Federal Highway Administration, the FTA, AASHTO, APTA, and the

Community Transportation Association of

America, should ensure that future transit

facility designs incorporating saw-tooth bus

parking bays, or other types of designs that

direct errant vehicular traffic toward pedestrianoccupied areas, include provisions for positive

separation between the roadway and pedestrian

areas sufficient to stop a bus operating under

normal parking area speed conditions from

progressing into the pedestrian area.

Further, to ensure that the significance of

this issue is appreciated within the public

transport industry, the Safety Board believes

that APTA and the Community Transportation

Association of America should notify their

memberships of the circumstances of the

Normandy, Missouri, accident of June 11, 1997,

and encourage them to retrofit any existing

facilities that incorporate saw-tooth bus parking

bays or other types of designs that direct errant

vehicular traffic toward pedestrian-occupied

areas to include provisions for positive

separation between the roadway and pedestrian

areas sufficient to stop a bus operating under

normal parking area speed conditions from

progressing into the pedestrian area.

Postaccident Actions

After the accident, the BSDA took

immediate action to address the safety problem

posed by inadequate protection between bus

parking and pedestrian areas. The BSDA

installed barriers at all its facilities with sawtooth parking bay layouts. Bollards16 designed to

prevent low-speed overruns were placed at the

forward ends of all saw-tooth bus parking

spaces at each of the four stations with sawtooth bus bays. Such bollards will be included in

the designs of future BSDA stations. Safety

Board investigators examined the bollard

installations and found them adequate to have

stopped the bus involved in this accident from

reaching the pedestrian area. Therefore, the

Safety Board concludes that, had the positive

separation barriers now installed at the

Normandy station been in place at the time of

the accident, the collision with the pedestrians

would not have occurred.

The Safety Board is aware that other transit

jurisdictions have used means other than

bollards for providing positive separation

between buses and pedestrian areas. The Safety

Board appreciates that site- or system-specific

approaches to positive separation that provide

for adequate pedestrian safety can be

successfully developed and employed by transit

authorities. The Safety Board does not intend to

prescribe any particular means of positive

separation, so long as the means selected are

effective in ensuring pedestrian safety.

 

16A single bollard is designed to stop a 36,000-pound

vehicle traveling at 4 mph. Three bollards of concretefilled, 8-inch-diameter, heavy-wall steel pipe are used at

each parking space. The pipe is set vertically in a 6-foot,

auger-drilled hole, and retained by reinforced concrete.
16

Findings

1. Neither weather nor vehicle conditions were

factors in this accident.

2. Activation of the emergency stop switch

could not have averted this accident.

3. The driver trainee was not fatigued,

impaired, or suffering from any medical

conditions that may have affected her

performance.

4. The driver trainee misapplied her foot to the

accelerator pedal, thereby causing the

unintended acceleration of the bus.

5. A combination of factors contributed to the

driver trainee’s pedal misapplication.

6. Once the bus began to accelerate, the driver

trainee did not have sufficient time to avoid

the encroachment onto the pedestrian

platform.

7. The excessive steering wheel lash of the

accident bus did not contribute to the

accident.

8. The current design guidelines for saw-tooth

parking bay configurations commonly

followed by the transit industry fail to

provide adequate pedestrian safety.

9. Had the positive separation barriers now

installed at the Normandy station been in

place at the time of the accident, the

collision with the pedestrians would not

have occurred.

Probable Cause

The National Transportation Safety Board

determines that the probable cause of this

accident was the driver trainee’s misapplication

of the accelerator, resulting in the bus’s override of the curb and travel onto the occupied

pedestrian platform. Contributing to the deaths

and injuries was the absence of effective

positive separation between the transit facility

roadway and the station’s pedestrian platform.

CONCLUSIONS
17

As a result of its investigation of this

accident, the National Transportation Safety

Board makes the following safety

recommendations:

— to the Federal Highway Administration:

Ensure, in cooperation with the Federal

Transit Administration, the American

Association of State Highway and

Transportation Officials, the American

Public Transit Association, and the

Community Transportation Association

of America, that future transit facility

designs incorporating “saw-tooth” bus

parking bays, or other types of designs

that direct errant vehicular traffic

toward pedestrian-occupied areas,

include provisions for positive

separation between the roadway and

pedestrian areas sufficient to stop a bus

operating under normal parking area

speed conditions from progressing into

the pedestrian area. (H-98-1)

— to the Federal Transit Administration:

Ensure, in cooperation with the Federal

Highway Administration, the American

Association of State Highway and

Transportation Officials, the American

Public Transit Association, and the

Community Transportation Association

of America, that future transit facility

designs incorporating “saw-tooth” bus

parking bays, or other types of designs

that direct errant vehicular traffic

toward pedestrian-occupied areas,

include provisions for positive

separation between the roadway and

pedestrian areas sufficient to stop a bus

operating under normal parking area

speed conditions from progressing into

the pedestrian area. (H-98-2)

— to the American Association of State

Highway and Transportation Officials:

Ensure, in cooperation with the Federal

Highway Administration, the Federal

Transit Administration, the American

Public Transit Association, and the

Community Transportation Association

of America, that future transit facility

designs incorporating “saw-tooth” bus

parking bays, or other types of designs

that direct errant vehicular traffic

toward pedestrian-occupied areas,

include provisions for positive

separation between the roadway and

pedestrian areas sufficient to stop a bus

operating under normal parking area

speed conditions from progressing into

the pedestrian area. (H-98-3)

— to the American Public Transit Association:

Ensure, in cooperation with the Federal

Highway Administration, the Federal

Transit Administration, the American

Association of State Highway and

Transportation Officials, and the

Community Transportation Association

of America, that future transit facility

designs incorporating “saw-tooth” bus

parking bays, or other types of designs

that direct errant vehicular traffic

toward pedestrian-occupied areas,

include provisions for positive

separation between the roadway and

pedestrian areas sufficient to stop a bus

operating under normal parking area

speed conditions from progressing into

the pedestrian area. (H-98-4)

Notify your members of the

circumstances of the Normandy,

Missouri, accident of June 11, 1997, and

encourage them to retrofit any existing

facilities that incorporate saw-tooth bus

parking bays or other types of designs

that direct errant vehicular traffic

toward pedestrian-occupied areas to

RECOMMENDATIONS
18

include provisions for positive

separation between the roadway and

pedestrian areas sufficient to stop a bus

operating under normal parking area

speed conditions from progressing into

the pedestrian area. (H-98-5)

— to the Community Transportation

Association of America:

Ensure, in cooperation with the Federal

Highway Administration, the Federal

Transit Administration, the American

Association of State Highway and

Transportation Officials, and the

American Public Transit Association,

that future transit facility designs

incorporating “saw-tooth” bus parking

bays, or other types of designs that

direct errant vehicular traffic toward

pedestrian-occupied areas, include

provisions for positive separation

between the roadway and pedestrian

areas sufficient to stop a bus operating

under normal parking area speed

conditions from progressing into the

pedestrian area. (H-98-6)

Notify your members of the

circumstances of the Normandy,

Missouri, accident of June 11, 1997, and

encourage them to retrofit any existing

facilities that incorporate saw-tooth bus

parking bays or other types of designs

that direct errant vehicular traffic

toward pedestrian-occupied areas to

include provisions for positive

separation between the roadway and

pedestrian areas sufficient to stop a bus

operating under normal parking area

speed conditions from progressing into

the pedestrian area. (H-98-7)

BY THE NATIONAL TRANSPORTATION SAFETY BOARD

JAMES E. HALL

Chairman

ROBERT T. FRANCIS II

Vice Chairman

JOHN A. HAMMERSCHMIDT

Member

JOHN J. GOGLIA

Member

GEORGE W. BLACK, JR.

Member

February 19, 1998