Introduction to Transportation Engineering

A: 10 seconds at 80 km/h is ~22 m/s, so you travel ~220 m before full braking even starts. From 22 m/s to zero at 0.5 m/s² takes ~44 s and another ~480 m. You're already near 700 m before allowing for any gradient or brake build‑up losses, so answers below that drop a term, while the multi‑kilometre answer assumes an order‑of‑magnitude weaker decel than typical freight air brakes.

A: A minimum axle shunt threshold is the hard boundary here. Track circuits and the downstream barrier logic only react to shunted occupancy; if the vehicle doesn't shunt, the system behaves as if the track is clear. Barriers still address road user behaviour when activated, and signals protect train‑to‑train separation, but the unshunted presence itself stays invisible.

A: Axle load magnitude, not ESAL count, drives distress here. Rigid pavement spreads load with slab action, and slow speeds remove the viscoelastic benefit asphalt normally enjoys. Flexible options look tempting due to volume, but they accumulate rutting and shoving under static and turning loads long before fatigue governs.

A: The boundary is between cold checks and powered tests. Verifying point‑to‑point continuity before energization catches cross‑wires and mis‑terminations that functional tests can mask. Only after that do powered I/O checks and simulated inputs make sense; jumping ahead exposes you to unsafe false clears.