########  Experimental Evaluation of Retroreflective Markings on Rail Cars at Highway-Railroad Grade Crossings 

by

Joseph Conti and Thomas B. Sheridan Jordan Multer

Human-Machine Systems Laboratory Operator Performance and Safety
Analysis Division

Massachusetts Institute of Technology John A. Volpe National
Transportation Center

Cambridge, MA 02139 Cambridge, MA 02139

Abstract

> Every year in the United States, hundreds of accidents occur at grade
> crossings due to motor vehicles colliding with trains. Some of these
> accidents take place at night in rural areas. One proposed solution to
> prevent such accidents involves mounting retroreflective material on
> the sides of trains so that a vehicle's headlights will illuminate the
> reflectors and make the train more conspicuous. The objective of this
> research was to determine which train mounted reflector pattern gives
> an approaching driver the best train recognition. Four reflector
> patterns were selected for this study, and a computer-based nighttime
> driving simulator was developed. The experiment involved a driving
> task in which the motorist encountered numerous grade crossings. The
> recognition distance between the train and subject's position was
> recorded and analyzed.

# Introduction

Defined as the intersection of a highway and railroad track, grade
crossings exist at over 168,000 locations throughout the United States
(Federal Railroad Administration, 1994). Unfortunately, many accidents
occur at grade crossings involving the collision of motor vehicles and
train consists. In 1996 there were over 1,183 motor vehicle run into
train (RIT) accidents, 613 of which occurred during nighttime conditions
(Federal Railroad Administration, 1996). Some of these accidents occur
in rural areas where little ambient light exists except for the
motorist's headlights. In addition, the dark color of typical freight
cars and the accumulation of dust and grime makes the task of train
recognition even more difficult.

The Federal Railroad Administration (FRA) has sponsored studies
exploring many methods to prevent such accidents including train mounted
incandescent/strobe lights, paint schemes, and audible warning devices
(Carroll, Multer, & Markos, 1995; Aurelius & Korobow, 1971; Carroll,
Hitz, Knable and Passera, 1998). A promising alternative method involves
mounting retroreflective material on the sides of train cars so that the
motorist's headlights will illuminate the reflectors giving the driver
adequate knowledge that a train is passing through the grade crossing.

# Prior Research

In 1996, the FRA sponsored a study conducted by the University of
Tennessee to explore various reflector patterns (colors and
configuration) to improve the nighttime conspicuity of trains. (Ford,
Richards, & Hungerford, 1996). This study concluded that:

-   A standardized retroreflector pattern is beneficial to train
    recognition.

-   The pattern should be made of red and white reflectors.

-   The pattern should not be confused with roadway signs or reflectors
    from other objects (i.e. trucks).

-   The pattern should communicate the size of the rail car through
    outlining or an even distribution.

With that in mind the John A. Volpe National Transportation Systems
Center (Volpe Center) proposed four reflector patterns to evaluate using
a driving simulator. These four reflector patterns: *massed outline*,
*vertical bars*, *variable vertical bars*, and *horizontal bars* are
presented in Figures 1 and 2 on the hopper cars and flat cars,
respectively. These patterns were chosen to represent a spectrum of
reflector layout strategies; namely distributing the reflectors along
the train car (horizontal bars and vertical bars), lumping them towards
the ends (massed outline), or a combination of the two (variable
vertical bars). In this study all four hopper car reflector patterns
each used exactly 144 square inches of red reflector material and 144
square inches of white reflector material (see Figure 1). The flat car
patterns each used exactly 72 square inches of red reflector material
and 72 square inches of white reflector material (see Figure 2). The
patterns in Figures 1 & 2 are all comprised of reflector strips 4 inches
wide with varying length.

A preliminary \"static\" experiment was conducted to determine which of
the four hopper/flat train reflector patterns described in Figures 1 & 2
gave the best train recognition. Participants were located at a fixed
location, 500 feet from the grade crossing. Numerous scenes simulating a
grade crossing and road intersection were presented. In some of these
scenes, a truck or train passed through the intersection and the
subjects were asked to identify the object. Each scene lasted 500
milliseconds and was followed by two questions asking what the subject
saw and how confident they were of their decision. Data from the
experiment were then analyzed using the receiver operating
characteristic (ROC) curve from Signal Detection Theory. Comparing the
ROC curve of the four different reflector styles yielded no notable
difference in performance (Conti, 1998).

The objective of this experiment was to determine which of the four
reflector patterns in both Figures 1 and 2 best facilitates the task of
train recognition with the motorist and train in motion . The patterns
were compared against patterns found on trucks, with which they might be
confused. Currently, the U.S. Code of Federal Regulations requires that
"not less than half of the length of the \[truck\] tractor trailer truck
is covered \[with reflectors\] and the spaces are distributed as evenly
as practicable" (49 USC 571.108). Figure 3 depicts the four truck
reflector patterns utilized in this study. These truck reflector
patterns were chosen to represent the typical patterns used by trucking
companies and manufacturers.

![](media/image1.png)

![](media/image3.png){width="3.638888888888889in"
height="1.6791666666666667in"}Figure 1. Hopper Car Reflector Patterns
Figure 2. Flat Car Reflector Patterns

Figure 3. Truck Reflector Patterns

# 

# Driving Experiment

#### Objective

The purpose of this experiment was to determine which of the four
reflector patterns described in Figures 1 & 2 gives the best train
recognition under a normal driving task on a dark rural road. As the
participants drove a car simulator, they encountered numerous objects
(i.e. grade crossings, road intersections with trucks or cars, traffic
lights, etc.) and subsequently reported what they recognized. Voice
recognition software recorded the subject's response, and the simulator
software determined the distance of recognition.

Apparatus

![](media/image4.jpeg){width="3.5in" height="2.238888888888889in"}A
driving simulator was created with the purpose of examining the
different train reflector patterns. This desktop simulator included a
personal computer for generating the vehicle dynamics and visual
scenery, a steering wheel, pedal controls, and driving dynamics to
simulate a vehicle traveling on a typical two-way American rural road.
The road was approximately 40 miles long and contained 22 grade
crossings; 20 of which had either flat cars or hopper cars passing
through. In addition, road markings, speed limit signs, intersection
signs, grade crossings signs, and traffic lights were rendered so that
this road conformed to U.S. regulations. The posted speed limit was 50
mph and most subjects completed the driving task in about an hour. Each
grade crossing contained the minimum sign requirements: a railroad
warning sign and a crossbuck sign. No other grade crossing features such
as flashing lights or reflectorized gates were included; this was done
to minimize the conspicuity of the grade crossing. Also, a forest of
trees was displayed on both sides of the road at all times so that the
subjects were forced to use the scenery directly in front of them to
recognize objects.

A sample screen output of the driving simulator is shown in Figure 4. A
speedometer was displayed along with the special words the subjects
could speak to signal what was seen. The experimental setup is displayed
in Figure 5

Figure 4. View of Driving Simulator

Figure 5. Experiment II Apparatus

#### Experimental Design

In this experiment, subjects drove a car for about one hour along a dark
rural road. On this road were many objects including automobiles,
lights, signs, trains, and trucks. When the subject recognized any of
the aforementioned objects he or she would say the word *car*, *light*,
*sign*, *train* or *truck* depending on what was recognized. Voice
recognition software recorded the subject's response and compared it
with what objects were really in the road. The distances from these
objects when the subject recognized them was also recorded. The subjects
viewed 22 grade crossings (20 of which had trains passing through), 40
cars, 20 trucks, and 4 traffic lights in the experiment.

######### 

#### Independent Variable

The independent variable was the type of reflector pattern and train car
thus giving ten possible combinations as shown in Table 1. The flat car
used the same patterns as the hopper car, but only half the amount of
material was used. Each of these variables was displayed to the subject
twice; therefore, each subject viewed a total of 20 trains during the
experiment.

###### 

+-------------------+--------------------+----------------------------+
| **Train Type**    |                    | #                          |
|                   |                    | ######## Reflector Pattern |
+-------------------+--------------------+----------------------------+
| **Hopper Train**  | **Flat Train**     |                            |
+-------------------+--------------------+----------------------------+
| 1                 | 6                  | Massed Outline             |
+-------------------+--------------------+----------------------------+
| 2                 | 7                  | Vertical Bars              |
+-------------------+--------------------+----------------------------+
| 3                 | 8                  | Variable Vertical Bars     |
+-------------------+--------------------+----------------------------+
| 4                 | 9                  | Horizontal Bars            |
+-------------------+--------------------+----------------------------+
| 5                 | 10                 | Unreflectorized            |
+-------------------+--------------------+----------------------------+

Table 1. Experiment II: Independent Variables

#### Dependent Variable

The dependent variable was the distance at which the subject recognized
the train and was measured using voice recognition software. If the
subject did not recognize the train or incorrectly recognized the train
as another object (i.e. truck or car ) an error was recorded.

#### Participants

A total of twenty-two people participated in the experiment, all of whom
were licensed drivers with vision better than 20/40. The subject's ages
ranged from 18 to 60 years with a mean of 37 years and standard
deviation of 13; 65% of the subjects were male. Seventeen of the
twenty-two subjects were volunteers from the Volpe Center and the
remaining participants were undergraduates paid \$10 per hour to
participate.

#### Instructions and Treatment of Subjects

The entire experiment for each subject lasted less than two hours. The
subject first read a brief description of the experiment, and then the
voice recognition software was trained to his or her voice. This
involved the subject saying the words *car*, *light*, *sign*, *train*,
and *truck* for about two minutes into a headset microphone. The subject
then practiced driving for about 7 minutes without the microphone. A
practice course allowed the subject to drive in an oval, get accustomed
to the controls, and see the various objects present in the experiment.
When the subject was comfortable with the driving task, he or she was
given the microphone and subsequently practiced driving while speaking
the various words. The subject continued this practice until he or she
was ready to begin the experiment. On average, participants practiced
this task for approximately ten minutes. During the experiment, the
experimenter was in an adjacent room and could communicate with the
subject using a walkie-talkie. Subjects were never told the purpose of
the experiment.

#### Results

Figure 6 plots reflector pattern versus recognition distance. The
recognition distances were computed by averaging the data from all
twenty-two subjects in the experiment. The standard deviation is
represented by the error bars in Figure 6. An analysis of variance
indicated that the mean distance of the hopper car is significantly
larger than the flat car (p \< .001). A Newman-Keuls post-hoc comparison
test with respect to the hopper reflector yielded a significant
difference (p \< .05) between the groups {Massed Outline, Vertical Bars,
Horizontal Bars}, {Variable Vertical Bars, Horizontal Bars}, and
{Unreflectorized} where the first group had the highest recognition
distances. There was no significant difference within these groups. For
the flat car, a significant difference (p \< .05) existed between the
groups {Vertical Bars, Horizontal Bars}, {Massed Outline, Variable
Vertical Bars}, and {Unreflectorized} where the first group had the
highest recognition distances, but there was no significant difference
within these groups (p \> .05).

![](media/image5.wmf)

Figure 6. Reflector Type versus Recognition Distance

The errors from the driving experiment are compiled in Table 2. The top
row of the table indicates what object (truck, car, or nothing) the
subject perceived the train as, and the first column indicates the type
of train reflector pattern displayed when the error occurred.

  -------------------------- ------------- --------- ------------ -------------
  **Hopper Car Errors**      **Nothing**   **Car**   **Truck**    Total

  **Massed Outline**         0             0         0            0

  **Vertical Bars**          0             0         0            0

  **Variable Vertical Bars** 0             0         0            0

  **Horizontal Bars**        0             0         2            2

  **Unreflectorized**        4             0         3            7

  Total                      4             0         5            9
  -------------------------- ------------- --------- ------------ -------------

  -------------------------- ------------- --------- ------------- -------------
  **Flat Car Errors**        **Nothing**   **Car**   **Truck**     Total

  **Massed Outline**         0             1         2             3

  **Vertical Bars**          0             0         0             0

  **Variable Vertical Bars** 0             0         0             0

  **Horizontal Bars**        0             0         1             1

  **Unreflectorized**        8             1         1             10

  Total                      8             2         4             14
  -------------------------- ------------- --------- ------------- -------------

Table 2. Subject Errors

# Discussion

Figure 6 along with the statistical analyses clearly indicates that
reflectorized trains were recognized at farther distances than
unreflectorized trains, for both the hopper and flat train cars.
Furthermore, the Newman-Keuls comparison test shows that the reflector
groups {Massed Outline, Vertical Bars, Horizontal Bars} and {Vertical
Bars, Horizontal Bars} performed the best with respect to the hopper and
flat cars. Common to both of these groups is the vertical bar and
horizontal bar reflector patterns, which both have reflectors
distributed along the base of the train car as opposed to the massed
outline and variable vertical bars patterns which are lumped towards the
ends (see Figures 1 and 2).

However, according to Table 2, three errors occurred with the horizontal
bar pattern but none occurred with the vertical bar pattern. Moreover,
these errors all involved subjects incorrectly identifying the train as
a truck. Since the study by Ford et al. (1996) recommended a
standardized train reflector pattern which minimizes confusion with
other objects (i.e. truck), these results suggest that the vertical
patterns may result in less confusion than the horizontal pattern.

Interestingly, in the debriefing questionnaire subjects responded
favorably with the massed outline reflector pattern on the hopper car
but unfavorably with the same pattern on the flat car. This agrees with
the experimental results in which a comparison test placed the massed
outline pattern in the group with the highest hopper recognition
distance and lowest flat train recognition distance. Therefore, the
massed outline reflector pattern only performed well with train cars
having a substantial height dimension available for marking (i.e. hopper
car).

# Conclusion

The experiment based on a realistic nighttime driving simulator
concluded that the vertical bar reflector pattern yielded better train
recognition performance than the horizontal, massed outline, or variable
vertical patterns. Moreover, a distributed pattern has better train
recognition qualities than a massed pattern on the flat car. This does
not hold true for the hopper car which introduces another dimension
(height) available for mounting reflectors.

# References

Aurelius, J. P. & Korobow, N. (1971). The Visibility and Audibility of
Trains Approaching Rail and Highway Grade

Crossings, Report No. FRA-RP-71-2. Washington, DC: U.S. Department of
Transportation, Federal Railroad

Administration.

Carroll, A., Hitz, J.S. Knable, N. & Passera, A.L. (1998). *Guidelines
for Highway-Railroad Grade Crossing Illumination.* Washington, DC: U.S.
Department of Transportation, Federal Railroad Administration

Carroll, A., Multer, J., & Markos, S. H. (1995). Safety of
Highway-Railroad Grade Crossings: Use of Auxiliary

External Alerting Devices to Improve Locomotive Conspicuity, Report No.
DOT-VNTSC-FRA-95-10.

Washington, DC: U.S. Department of Transportation, Federal Railroad
Administration.

Conti, J. (1998). Experimental Evaluation of Retroreflective Markings on
Trains at Grade Crossings. S.M. Thesis,

MIT.

Ford, R. E., Richards, S. H., & Hungerford, J.C. (1996). Evaluation of
Retroreflective Markings To Increase Rail

Car Conspicuity. U.S. Department of Transportation , Volpe National
Transportation Center.

U.S. Code of Federal Regulations, 49 Part 571.108, Section 5.7.1.4.2

Federal Railroad Administration, Office of Safety. Highway-Rail Crossing
Accident/Incident and Inventory

Bulletin. (1996). Washington, DC: U.S. Department of Transportation.

Federal Railroad Administration, Office of Safety. Highway-Rail Crossing
Accident/Incident and Inventory Bulletin

#60. (1994). Washington, DC: U.S. Department of Transportation