Track Capacity Calculator

Railroad line capacity is fundamentally governed by headway — the minimum safe time gap between successive trains — which this calculator sets from your chosen signal system: 30 minutes for dark territory (train-order operation with no signals), 12 for Automatic Block Signaling, 8 for Centralized Traffic Control, and 4 for PTC/ERTMS systems capable of moving-block operation. Theoretical capacity is simply the operating minutes per day divided by that headway, but real railroads never run at theoretical capacity — delays, recovery time, and mixed traffic mean practical capacity is modeled here at 65% of theoretical. Single-track segments get an additional penalty: trains running in both directions must meet and pass at sidings, so the calculator adds an assumed 15-minute meet delay scaled by how many meets are likely across the segment (estimated from segment length assuming a siding roughly every 15 miles), effectively inflating the headway. Multiple-track corridors are modeled as track pairs handling one direction each at the practical factor, with any single leftover track penalized further for its single-track meet constraints.

The tonnage outputs simply multiply daily/annual train counts by an assumed average 5,000-ton train. Two outputs are assumptions rather than results and should be read that way: Velocity factor is a flat 1 − 0.3 × the same assumed 65% utilization, so it never moves with anything you enter, and Delay index — minutes of delay per 100 train-miles — is a rule-of-thumb 15 min for single track or 5 min for multiple track, scaled by that same constant velocity factor, so it responds only to your track count and not to how hard the corridor is worked. A corridor-specific version of either would need a declared trains-per-day-actually-operated figure to compare against the calculated capacity. All of the specific constants here — practical factor, meet delay, siding spacing, average train weight — are industry rules of thumb, not measurements of your specific corridor, so use this for conceptual capacity planning and comparing signal-system upgrades rather than as an operating commitment.