This page now presents only a transparent speed-times-entered-time scenario. It no longer labels that arithmetic as a required approach distance or implies that three user-entered intervals design a railroad crossing warning system.
Declared Constant-Speed Distance Scenario
Enter a declared train speed and three independently declared time intervals. The worksheet adds the intervals and applies constant-speed distance arithmetic; it does not assess warning adequacy or design a crossing.
Equation Used
- Train speed is declared and remains constant for the entire entered interval.
- The three time values are independent declarations and are not generated from a crossing standard or site study.
- The animated gate and train are normalized illustrations of the entered timeline only.
- Actual detection can account for direction, speed, distance and changes in motion in ways this ledger does not model.
- Crossing geometry, track circuits, traffic signal interconnection, vehicle and pedestrian clearance, multiple tracks and failure modes are excluded.
- Design, installation, testing, operation, compliance and safety conclusions are excluded.
Retains exact constant-speed arithmetic while removing the implication that user-entered times design or validate a regulated grade-crossing warning system.
Active crossings combine detection, logic and warning devices
The FHWA/FRA Highway-Rail Crossing Handbook describes active warning systems and refers approach-length calculations to specialized design guidance. FRA explains that constant-warning-time systems measure train speed and distance to estimate arrival time.
The animation here is only a normalized timeline: it does not simulate a predictor, track circuit or controller.
Use this only as a declared scenario ledger
The worksheet converts mph to ft/s, adds three entered intervals and reports the constant-speed distance traveled over that total.
It cannot establish required warning time, approach length, clearance, equipment or compliance.
Constant-speed arithmetic
These identities do not model acceleration, deceleration, stopping or site-specific warning logic.
A transparent entered scenario
At a declared 40 mph with entered intervals of 20, 12 and 5 seconds, T=37.0 s, converted speed=58.7 ft/s and constant-speed distance=2171 ft (662 m).
A distance scenario is not a crossing design
The FHWA/FRA handbook identifies track clearance, nearby intersections, users and other conditions that can affect warning-system design. FRA also notes that speed changes after detection can alter actual warning time.
The former universal approach-distance, timing, installation and operating claims are removed.
Crossing-ledger questions
Is the displayed distance a required approach length?
No.
Does the calculator test a 20-second requirement?
No.
Does it simulate constant-warning-time equipment?
No.
Who determines warning devices?
FRA notes that states and railroads cooperate on the needed devices, supported by applicable standards and site studies.
Grade-crossing references
- FHWA/FRA Highway-Rail Crossing Handbook, Third Edition: active-warning context and specialized approach-length design references.
- FRA Constant Warning Time Detection: operating concept, limitations and site-study factors.
- FRA Railroad Crossing Safety: states and railroads cooperate to determine needed warning devices.
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