FEDERAL HIGHWAY ADMINISTRATION • OFFICE OF MOTOR CARRIERS

FHWA Contact: Chuck Rombro, HIA-20, (202) 366-5615

1996 National Fleet Safety Survey

Introduction

Approximately 2 million roadside inspections of commercial motor vehicles (CMVs) are

conducted annually, primarily through the joint Federal and State Motor Carrier Safety

Assistance Program (MCSAP). Vehicles and drivers with serious safety problems are

placed out-of-service (OOS) and are not allowed to continue operations until the 

condition is corrected. Inspections are not conducted randomly; inspectors focus on

vehicles that pose safety risks. While this is a reasonable enforcement strategy, it limits

the Federal Highway Administration’s (FHWA) ability to use these data to estimate the

“true” OOS rate, i.e., the percentage of vehicles and drivers that would be placed OOS

if all vehicles were inspected. To estimate this rate, the FHWA conducted the National

Fleet Safety Survey (NFSS) in the summer of 1996, during which a number of States

randomly inspected CMVs.

The FHWA decided to take advantage of this unique survey to gather information 

not regularly obtained during inspections, including data on driver training and 

experience. In addition, because of widespread interest in the safety of hazardous

material (HM) shipments, vehicles carrying placardable quantities of HM were 

oversampled, whereby an extra number of HM vehicles was chosen for inspection.

This Analysis Brief presents a summary of the 1996 National Fleet Safety Survey which

is fully documented in a separate report (FHWA-MC-98-015).

Research Methodology

A three-stage sample design was employed: States were selected in the first stage,

inspection locations in the second, and trucks in the third stage.

Stage 1: States

Due to practical considerations, only States that were willing to participate were 

eligible for selection in the first stage of selection. The 17 States that volunteered to

participate in the NFSS were divided into 4 strata, based on their past overall Level 1

OOS rates from MCSAP inspections: 

• Less than 32 percent of vehicles placed OOS

• 32 percent to 39 percent of vehicles placed OOS

• 39 percent to 46 percent of vehicles placed OOS

• Over 46 percent of vehicles placed OOS

Three States were purposively (not randomly) selected from each strata, and one State

withdrew from the survey, leaving 11 participants. The FHWA attempted to ensure the

sample was geographically disperse, given the limited number of candidate States.

Stage 2: Inspection Sites

Fixed and non-fixed inspection sites were selected within each State from each of four

road and area types:

• Rural Interstate roads

• Rural Non-Interstate roads

Analysis Brief

The vision of the Office of

Motor Carriers (OMC) is to

help move people, goods, and

commercial motor vehicles on

our Nation’s highways in the

most efficient, economical,

and crash-free manner possible. The goal of OMC’s Office

of Information Analysis is to

develop and maintain systems

for collecting and analyzing

motor carrier data and to 

disseminate information 

concerning the motor carrier

industry.

The Analysis Division analyzes

motor carrier data pertaining

to crashes, inspections, compliance reviews, and drug 

and alcohol testing; supports

research on the effectiveness

of OMC programs, such as

roadside inspections and 

compliance reviews; and helps

States to comply with Federal

size and weight statutes for

trucks.

Office of Motor Carrier Research

and Standards

400 Seventh Street, SW

HCS-30; Room 3107

Washington, DC 20590
• Urban Interstate roads

• Urban Non-Interstate roads

Because of practical difficulties in selecting sites,

selection of the sites was left to the States. Although

the selection of sites was purposive rather than 

random, States were instructed to select as many 

different kinds of sites as possible and were given a

minimum number of sites to be selected within each

road-type category. 

Stage 3: Inspections

The required number of inspections was allocated 

to the States loosely following the rule of optimal 

allocation, using vehicle miles of travel (VMT) as a 

size measure, so that States with more truck travel

conducted a greater number of inspections. States

were asked to initially sample the third eligible truck.

Thereafter, States were to sample the next truck 

available, and to continue in this fashion until the

completion of the shift. 

To ensure that a sufficient number of HM trucks was

inspected, States were requested to set aside one day

for inspecting HM trucks exclusively. However, not all

States followed this procedure, and some of those 

that did still did not inspect a large enough number

of HM trucks to allow for viable estimates by road

and area type.

Two samples were generated: an “all-trucks sample”

which included all inspections conducted in the 

survey, and an “HM-only sample” which was limited

to inspections conducted on the day only HM trucks

were inspected. Some States had difficulty meeting

the allocated sample sizes in certain road and area

types, particularly on urban, non-interstate roads. The

number of inspections conducted by each State in

each road and area type is shown in table 1.

Estimation

Estimates of the OOS rate were calculated using 

formula 1. Because the value of Nh (the number of

trucks operating in different sampling strata) is

unknown, we used truck VMT as a proxy. Since the

assumption that VMT is highly correlated with Nh is a

reasonable one, only minimal bias may be introduced

into the estimator.

Results

Over 10,000 level 1 inspections were conducted in the

NFSS. The overall OOS rate was 32 percent: 29 percent

for vehicles and 5 percent for drivers. (The vehicle and

Formula 1. 

P = ( ∑ph x Nh ) ÷ ∑Nh

where,

Ph is the percentage of trucks that are OOS in stratum h,

Nh is the number of trucks in stratum h, and 

h is the stratum defined by the road and area type.

Table 1. 

Level 1 Inspections Conducted in the “All-Trucks Sample” 1996 National Fleet Safety Survey

Rural Urban

State Interstate Non-Interstate Interstate Non-Interstate

California 175 77 731 227

Connecticut 180 174 34 49

Illinois 209 164 17 54

Kansas 112 221 31 53

Maryland 441 134 225 102

Missouri 2005 512 20 24

New Mexico 197 62 98 1

North Carolina 216 201 192 151

Ohio 512 267 106 66

Washington 219 435 171 110

Wisconsin 405 335 225 19

Total 4,671 2,582 1,850 856
driver rates do not add up to the overall 32 percent

total OOS rate because some instances were found

where both the vehicle and driver were OOS.) These

rates were slightly lower than the comparable fiscal

year 1996 MCSAP OOS rates, as was expected, and the

differences appear to be statistically significant at the

national level. Table 2 presents the national and

State-specific OOS rates from the NFSS and MCSAP. 

The most common OOS violations were brake related,

accounting for almost half of those found in the

NFSS. Approximately half of the brake violations were

for out-of-adjustment brakes. This distribution of 

violations was the same for HM vehicles.

The OOS rates differed slightly for different locations

or levels of driver experience. OOS rates were similar

for fixed and non-fixed sites, for day and night

inspections, for drivers with different levels of 

training and experiences, and with different types 

of loads. The differences in OOS rates across these

categories were not statistically significant. One 

interesting and statistically significant difference was

that drivers with 3 or fewer years of experience and

no training had a dramatically higher OOS rate than

drivers who had received some training: 51 percent

compared to 31 percent.

OOS rates were somewhat lower at urban than at

rural inspection sites. For interstates, urban sites had

an OOS rate of 30 percent compared to 33 percent at

rural sites; for non-interstates, rates were 29 percent

and 34 percent, respectively.

Based on the NFSS, approximately 7.2 percent of 

trucks carry placardable amounts of HM. Twentyseven percent of vehicles carrying HM were placed

OOS: 25 percent for vehicle violations and 4 percent

for driver violations. These numbers are somewhat

lower than found for all inspections, and the differences are statistically significant. For HM vehicles,

unlike the other vehicles in the survey, there was no

difference in the OOS rates between rural and urban

inspections. Seventy-eight percent of trucks requiring

HM registration had the correct documentation, and

these vehicles had a lower OOS rate than those lacking appropriate registration documentation.

Future Plans

A second NFSS was conducted in June and July of

1998, with about double the number of States participating. The results from this NFSS will be used to

refine the estimate of the true OOS rate, and to measure any change since 1996.

Table 2. 

1996 National Fleet Safety Survey and FY 1996 MCSAP Out-of-Service Rates (Level 1 Inspections)

Fleet Survey Results MCSAP Results

Total Driver Vehicle Driver Vehicle

State OOS Rate OOS Rate OOS Rate OOS Rate OOS Rate

California .22 .02 .21 .03 .26

Connecticut .31 .07 .27 .10 .51

Illinois .33 .12 .26 .05 .31

Kansas .35 .07 .30 .05 .33

Maryland .37 .04 .35 .05 .36

Missouri .37 .07 .34 .10 .46

North Carolina .36 .05 .32 .06 .32

New Mexico .39 .10 .34 .07 .41

Ohio .38 .09 .34 .12 .43

Washington .29 .04 .27 .05 .32

Wisconsin .30 .02 .29 .08 .37

Nation .32 .05 .29 .06 .32

Source: FHWA 1996 Fleet Survey and MCSAP FY96 Quarterly Report File
Researcher

This analysis was performed by

Star Mountain, Inc. 

3601 Eisenhower Avenue,

Alexandria, VA, 22304.

Telephone: (703) 960-7000.

Contract No.: DTFH61-94-Y00114.

Distribution

This Analysis Brief is being 

distributed according to a standard distribution. Direct distribution is being made to the

Regions and Divisions.

Availability

The final analysis report is now

available. Copies can be

obtained from the OMC’s

Office of Information Analysis,

Analysis Division. Telephone:

(202) 366-1861.

Key Words

trucks, out-of-service rates, survey, hazardous materials (HM). 

Notice

This Analysis Brief is disseminated under the sponsorship of

the Department of

Transportation in the interest

of information exchange. 

The Tech Brief provides a 

synopsis of the study’s final

publication. The Tech Brief

does not establish policies or

regulations, nor does it imply

FHWA endorsement of the conclusions or recommendations.

The U.S. Government assumes

no liability for its 

contents or their use.

September 1998

Publication No. FHWA-MCRT-98-004