Michael H.
Schrader, P.E.
Wilbur Smith
Associates, Inc.
John R.
Hoffpauer, AICP
Metroplan
In order to better allocate scarce regional transportation
resources when considering the construction of grade-separated highway-railway
crossings in
Michael H.
Schrader, P.E.
Wilbur Smith
Associates, Inc.
Phone: (214) 890-4460
Fax: (214)
890-7521
e-mail: mschrader@wilbursmith.com
John R.
Hoffpauer, AICP
Metroplan
Suite B
Phone: (501)
372-3300
Fax: (501)
372-8060
e-mail: jhoffpauer@metroplan.org
Paper No. 01-3051
Michael H.
Schrader, P.E.
Wilbur Smith
Associates, Inc.
John R.
Hoffpauer, AICP
Metroplan
One
roadway element that has always been of concern to traffic practitioners since
the mass popularization of the automobile as the preferred mode of travel is
the at-grade railroad crossing. Railroad
crossings are perceived by many to be among the most dangerous, if not the most
dangerous, of all the roadway elements.
Nowhere else on our roadway network is there a direct conflict between
vehicles of such different size and operating capability than at a railroad
crossing -- when a collision does occur, it is usually severe. In addition to the safety concerns of
at-grade crossings are the economic and environmental concerns. Delays at at-grade crossings contribute to
the loss of economic productivity, excessive wear-and-tear on vehicles, and the
inefficient use of non-renewable natural resources (e.g. fuel). In addition, inadequate maintenance of at-grade
crossings increases operational costs for both motorists and railroads. In short, at-grade crossings, and especially
poorly maintained crossings, can be detrimental to the economic vitality of a
community.
Because of these economic and safety
issues, it is often beneficial to replace an at-grade crossing with a
grade-separated one. The Interstate
system provided the upgrading of at-grade crossings along the nation’s trunk
highways. While the impact of the Interstate
system has been substantial in terms of mobility and economic vitality, the
Interstate system represents just a small fraction of the total road and
highway mileage, and correspondingly, the total number of at-grade railroad
crossings, across the nation.
Unfortunately, grade-separated rail crossings are
relatively expensive, and thus the prevalent railroad crossing is
at-grade. For many jurisdictions, the
cost of just one grade separation would consume several years’ worth of
operating budgets. The majority of the
member communities of Metroplan, the Metropolitan Planning Organization (MPO)
for
When deciding what kind of
methodology to use in evaluating potential highway-railway grade separation
locations, it was recognized that while benefit/cost ratios are important, they
should not be the only determinant in selecting where rail grade separations
should be located. It was decided to
attempt to develop and apply a range of evaluation factors in an effort to prioritize
highway-railway grade separation needs in the
Seven factors, both quantitative and qualitative, were identified as preliminary evaluators, and quantitative equivalents were established for each. These seven factors are: noise, community cohesion, safety, delay, accessibility, geographic distribution, and connectivity. Each factor is equated to yield comparable values between 0 and 1.
Train
horn noise is a significant quality-of-life issue in many communities across
the country. The
While the communities did not want to
impose Draconian measures such as the banning of the blowing of a train’s horn
within their corporate boundaries (due to the obvious safety concerns of such
an action), they did want to try to address the noise issue somehow. It was perceived by these communities that if
at-grade crossings were replaced by grade-separated ones, the trains would no
longer have to blow their horns, and thus the noise problem would be abated.
Because of these concerns about noise, it
was imperative to take into account noise in any evaluation of potential
highway-railway grade separation locations.
The Noise Factor, NF, is a
quantification of the impact of train horn noise on communities. The intent of this factor is to compare
at-grade rail crossings on the basis of the extent to which surrounding
communities are impacted by noise from the blowing of train horns.
The Noise
Factor, NF, is defined by the following equation:
NF = (P0.5 x ADTT) / 250 (Eq. 1)
where,
P0.5 = estimated
population within 0.83 km (0.5 miles) of the railroad along the length that the
whistle is blown and 0.42 km (0.25 miles) on either side of the railroad
crossing (in thousands)
ADTT = average daily train traffic
250 = constant
to generate a number between 0 and 1[1]
As population density in the
vicinity of the crossing is a component of this factor, NF for urban areas will
be higher than NF for rural areas, as more people are impacted by the noise.
Community cohesion is the sense of
“oneness” of a community—the greater the cohesion, the greater this
“oneness”. There are three basic levels
of community cohesiveness: fully cohesive,
non-cohesive, and semi-cohesive. A fully
cohesive community is one in which all sections of a community are
interdependent, analogous to the interdependence of a married couple. In
In the
communities of
The
Community Cohesion Factor,
where,
DA-B = Desire
to travel from A to B
DB-A = Desire
to travel from B to A
For a fully-cohesive community,
That motorists generally incur
travel-time delay costs when waiting for trains to clear at-grade crossings is
universally recognized. However, the
cost of time is not the only cost that may result from delaying motorists at
rail crossings. In communities without a
highway-railway grade separation, the time it takes for a train to pass could
be life threatening to a trauma victim on the way to a hospital emergency
room. Therefore, it is important to
determine which rail crossings have higher vehicular delay when evaluating
potential grade separation locations, due to the full range of social costs
associated with delay at grade crossings.
Previous research by others has been
incorporated into the Delay Factor (DF),
which is the final derivative of a series of equations provided in NCHRP Report 288[2]
based on the average
train length, the average train speed in the crossing, the railroad crossing
activation time, and the average annual train and vehicular traffic. (During
development of the delay factor, problems were encountered in using some of the
formulas reported in NCHRP Report 288. After communicating these problems, changes
were made to several of the report’s equations by one of its authors.[3] )
The DF is given by the following
equation:
DF = TD
/ 480 (Eq.
3.1)
where,
TD = total vehicular delay (in hours)
where,
V = number of vehicles delayed at crossing on an average
day
where,
AADT = annual average daily traffic
P = probability of vehicular delay during an average
day
P = M / 1440 (Eq. 3.4)
where,
M = number of minutes crossing is blocked on an average
day
where,
L = average train length (in km)
S = average train speed through crossing (in km/h)
60 = constant (minutes in an hour)
AT = typical RR crossing signal activation time (in
minutes)
ADTT = average daily train traffic
From Eq.
3.2,
D = average duration of delay per vehicle delayed (in
minutes)
D = M / ADTT / 2 (Eq. 3.6)
where,
M = number of minutes crossing is blocked on an average
day (from Eq. 3.5)
ADTT = average daily train traffic
In urban areas, it is relatively simple
to bypass an at-grade rail crossing that is occupied by a train. At many urban locations, a grade-separated
crossing is just a few blocks away. In
those locations, is it generally quicker
to bypass to the grade separation than to wait for the train. In these locations, then, the need for a
grade separation, with respect to a motorist’s ability to get from one side of
the tracks to the other when a train is occupying the crossing, is, for all
intents and purposes, moot.
This is not the case in suburban and
rural areas. Outside of the urban cores,
highway-railway grade separations are located miles apart, if they exist at
all. Thus, in these areas a motorist may
have to drive many miles in order to bypass an at-grade rail crossing occupied
by a train. In these locations, it is
not very practical to bypass to the nearest grade-separated crossing, as the
time required to bypass would be much greater than the time required to wait for
the train. It is in these locations that
accessibility becomes a significant issue.
The Accessibility
Factor (AF) measures the difference in distance between a route using an
at-grade crossing and a route using the nearest grade-separated crossing. Note that the distance for both the at-grade
crossing and the grade-separated crossing begins where the alternate route
leaves and end where the alternate route rejoins.
AF = (
D1 - D2
) / 24 (Eq. 4)
where,
D1 = detour distance -- distance using nearest
grade-separated crossing
D2 = through distance -- distance using the
at-grade crossing
24 = constant
(maximum ratio difference)
Because of the relatively high cost of
grade-separated rail crossings versus at-grade crossings, it is important to
locate these structures at the locations will they will receive the highest
usage. Intuitively, these locations will
be on facilities that connect major trip generators, be they states, cities, or
major employment centers within a community.
These facilities tend to be those of higher functional classification,
such as arterials, expressways, and freeways.
As the functional classification of a facility is easy to determine, the
Connectivity Factor (CF) uses
functional classification as a measure of connectivity. Specifically, CF is
CF = AADT / FC / 20,000 (Eq.
5)
where,
FC = Functional Classification Value, where
FC = 1 for a freeway;
FC = 2 for an expressway;
FC = 3 for a principal arterial;
FC = 4 for a minor arterial;
FC = 5 for a collector;
FC = 6 for a local street
AADT = annual average daily traffic
20,000 = constant to generate value
between 0 and 1
The jurisdiction of Metroplan consists of
four counties in
The east-west corridor connects
There was a concern expressed by some in
the
The GDF is defined as follows:
GDF = 1 - (
GS / TC ) (Eq. 6)
where,
GS = number of highway-railway grade
separations per km (mile) along the railroad subdivision in the subject county
TC = total number of at-grade and
grade-separated crossings per km (mile) along the railroad subdivision in the
subject county
1 = constant to prioritize low number of grade
separations
None of the other factors can evoke the
emotion, publicity, and urgency as the issue of safety. Accidents, and especially fatalities, tend to
be given extensive media coverage, thus evoking outrage in the community to fix
the problem to prevent further loss of life and property. Logically, then, safety has to be considered
when evaluating possible highway-railway grade separation locations.
The Safety
Factor, SF, is given by Equation 7.
SF = A / XD (Eq.
7)
where,
XD = type of warning device at
railroad crossing, where:
XD = 1 for Gates
XD = 2 for Flashing Lights
XD = 3 for Passive devices
A = predicted accidents per year (from FRA’s Railroad
Crossing Accident Prediction Formulas[4] or
comparable formulas). Data needed for the FRA formulas include:
1.
Type of warning device (passive, flashing lights, or
gates)
2.
AADT (annual average daily traffic)
3.
ADTT (average daily train traffic)
4.
Peak trains per day (number of trains per day during
daylight hours)
5.
Maximum timetable speed (in mph)
6.
No. of main tracks
7.
Highway paved? Yes or No
8.
Number of highway lanes
9.
Accident history (number of accidents in T years).
RESULTS
Although the factors were intended to generate
numbers of approximately equal magnitude within the range of 0 to 1, neither
outcome occurred; several values were slightly greater than one, and the
magnitude of the values varied widely from factor to factor. Thus, the inherent weighting of the various
factors was uneven. The values were
normalized so that the value ranges for each factor were approximately equal,
and all values were within the intended
range.
It should be noted, however, that the values for
The normalization of the raw values was a
three-step process. First, for each
factor, the maximum value was set equal to one, and all other values for that
factor were adjusted proportionally.
Second, the average of the values for each factor was set equal to the
highest average of values for any factor, and all values were adjusted
accordingly. The third and final
adjustment set the highest maximum value for any factor equal to one, and for
all factors all other values were adjusted proportionally. The resulting values ranged from 0 to 1
and yielded factors of approximately
equal weight.
CONCLUSIONS
This methodology produced results that were
deemed to be equitable and useful to the many jurisdictions and other
stakeholders that participate in the regional planning process in
Because the normalized values produce factors of
equal weight, it is simple to apply multipliers to individual factors to
produce customized weighting scenarios based on the priorities of the
communities involved. In the case of
While the normalized values of the factors are
useful in providing a snapshot comparison of different crossing locations, the
raw values are useful in detecting trends at a particular location or for a
particular factor. This type of trend
information is particularly useful when implementing long range comprehensive
planning strategies.
Finally, although some of the constants used in
the equations are based on data specific to
[1] Constants
for NF, AF, and CF based on data specific to
2 NCHRP Report 288, Evaluating Grade-Separated Rail and Highway Crossing Alternatives, Transportation Research Board, NRC, Washington, D.C., June 1987, “Appendix A, User’s Guide To The Decision-Making Framework”, pp. 19-38.
[3]
In March 1996, Alan Brick-Turin of Frederic R. Harris, Inc. (
[4] DOT/FRA/OS-87/10, Rail-Highway Crossing Resource Allocation Procedure –User’s Guide, Third Edition, U.S. Dept. of Transportation, Federal Railroad Administration, Washington, D.C., August 1987.