Terminology


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Alternative Safety Measures (ASM)

A safety system or procedure, other than an SSM, established in accordance with 49 CFR Appendix D to part 222 which is provided by the appropriate traffic control authority or law enforcement authority and which, after individual review and analysis by the Associate Administrator, is determined to be an effective substitute for the locomotive horn in the prevention of highway-rail casualties at specific highwayrail grade crossings.

Supplemental Safety Measures (SSM)

A safety system or procedure established in accordance with 49 CFR Appendix A to Part 222 which is provided by the appropriate traffic control authority or law enforcement authority responsible for safety at the highway-rail grade crossing, that is determined by the Associate Administrator to be an effective substitute for the locomotive horn in the prevention of highway-rail casualties.

Wayside Horn

A stationary horn located at a highway-rail grade crossing, designed to provide, upon the approach of a locomotive or train, audible warning to oncoming motorists of the approach of a train.  Is considered a one-for-one substitute to the train horn.  Can be used at any highway-rail grade crossing equipped with flashing lights, gates and constant warning time circuitry.  May be used within a Quiet Zone, to eliminate the associated risk index of the crossing on which it is installed, or utilized at a highway-rail grade crossing outside of a Quiet Zone to eliminate the routine sounding of the train horn.

Quiet Zone Risk Index (QZRI)

The measure of risk to the motoring public which reflects the Crossing Corridor Risk Index for a Quiet Zone (if horns are presently sounded at the crossings) and reduced risk due to implementation, if any, of SSMs, ASMs and/or Wayside Horns within the Quiet Zone.

Nationwide Significant Risk Threshold (NSRT)

The number reflecting a measure of risk, calculated on a nationwide basis, which reflects the average level of risk to the motoring public at public highway-rail grade crossings equipped with flashing lights and gates and at which locomotive horns are sounded.

Risk Index With Horns (RIWH)

The measure of risk to the motoring public when locomotive horns are routinely sounded at every public highway-rail grade crossing within a quiet zone.

Crossing Corridor Risk Index (CCRI)

The number reflecting a measure of risk to the motoring public at public grade crossings along a rail corridor, calculated in accordance with the procedures in Appendix D of the FRA’s Train Horn Rule document, representing the average risk at each public crossing within the corridor. This risk level is determined by averaging among all public crossings within the corridor, the product of the number of predicted collisions per year and the predicted likelihood and severity of casualties resulting from those collisions at each public crossing with the corridor.

Temporary Closure

Designed to provide for a Partial Quiet Zone, required under the new FRA train horn rule, allowing train horns not to be routinely sounded during certain hours of the day (10pm-7am) by eliminating vehicular access to the crossing.

Four-Quadrant Gate System

A system of gates designed to provide a full closure of the crossing eliminating the opportunity to drive around a single lowered gate.

Channelization Device

A traffic separation system made up of a raised longitudinal channelizer, with vertical panels or tubular delineators attached, that is placed between opposing highway lanes designed to alert or guide traffic around an obstacle or to direct traffic in a particular direction.

Non-traversable Curb

A highway curb designed to discourage a motor vehicle from leaving the roadway. Non-traversable curbs are used at locations where highway speeds do not exceed 40 miles per hour. The curbs must be at least six inches high.

One Way Street with Gate(s)

Gate(s) must be installed such that all approaching highway lanes to the public highway-rail grade crossing are completely blocked.

Permanent Closure

Permanently close the crossing to highway traffic.