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Section 4: The Texas Priority Index

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Introduction

The Texas Priority Index is used to prioritize projects qualifying for the Federal Railroad Signal Program. This section describes the index and the formulas used to calculate it.

The Texas Priority Index is re-calculated at least once per year for every public highway-rail grade crossing eligible for federal-aid program funds. TRF is responsible for calculating the index using data maintained and furnished by the Transportation Planning and Programming Division (TPP). These data include DOT crossing inventory information, vehicle and rail traffic, types of rail service, roadway information, school bus information, and crash data provided to TPP from the Department of Public Safety. The data are used in a formula to calculate the index rating for each crossing.

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Priority Index Formula

The Priority Index (PI) formula is

where:

V = average daily traffic — number of vehicles per day

T = number of trains in a 24-hour period

S = speed — maximum speed of the trains

Pf = protection factor — a factor weighted according to the type of existing traffic control device as shown in the following table:

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Existing Traffic Control Device

Protection Factor

Gates

0.10

Cantilever Flashers

0.15

Mast Flashers

0.70

Crossbucks or Other

1.00



A = number of crashes in the last five years to the 1.15 power (when A = 0 or A = 1, then A = 1)

EXAMPLE: COMPUTATION

V = 5000 v.p.d.

T = 12 trains/day

S × 0.10 = 6.0 ( S = 60 mph)

Pf = 0.70 (mast flashers)

A = 4.92 (4 crashes in last five years to the 1.15 power)

PI = 5000 (12) (6.0) (0.70) (4.92) (0.01)

PI= 12,398

More Than One Track. At locations with more than one track where main line and switching movements occur over the same crossing and at different speeds, a priority index is calculated for both the main line traffic and switching traffic, then added together to equal the total priority index for the crossing.

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School Bus Priority Index Formula

Priority ratings for unsignalized public crossings eligible for the Federal Railroad School Bus Signal Program are calculated using a special formula. (For a basic description of the program, see Section 2 of this chapter.)

The School Bus Priority Index (SBPI) formula is

where:

V = average daily school bus traffic

T = number of trains in a 24-hour period

S = speed — maximum speed of the trains

A = number of crashes in the last five years to the 1.15 power (when A = 0 or A = 1, then A = 1)

EXAMPLE: COMPUTATION:

V = 5 SB/day

T = 12 trains/day

S = 60 mph

A = 4.92 (4 crashes in last five years to the 1.15 power)

SBPI = 5 (12) (60) (4.92) (0.01)

SBPI = 1,771

More Than One Track. At locations with more than one track where main line and switching movements occur over the same crossing and at different speeds, a priority index is calculated for both the main line traffic and switching traffic, then added together to equal the total priority index for the crossing.

NOTE: The existing protection factor has been omitted from the school bus formula because only unsignalized crossings (crossings with crossbuck signs only) are eligible for this program.

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