How far does a train need to travel to stop?

The tragedies of two train collisions in Semarang and Bandar Lampung on Tuesday (18/7/2023) have garnered various public responses, one of which concerns the braking system in train transportation.

PT Kereta Api Indonesia (Persero), or KAI, explained why trains cannot stop suddenly in critical situations to avoid collisions.

KAI's VP of Public Relations, Joni Martinus, stated that trains require a certain distance to brake completely.

According to Joni, trains, by their technical characteristics, cannot brake suddenly like other land transportation.

“Therefore, we urge the public to be more vigilant and cautious before crossing level crossings,” Joni said in a press release on Friday (21/7/2023).

Furthermore, Joni mentioned several factors that prevent trains from braking suddenly. These include the length and weight of the train formation and the braking system itself.

Trains in Indonesia generally use an air brake system. This works by compressing and storing air until braking is needed.

“Even though trains are equipped with emergency brakes, these still cannot stop the train suddenly. These brakes only generate more energy and greater air pressure to stop the train faster,” Joni explained.

Several factors influence braking distance:

* Train speed: Higher speeds require longer braking distances.
* Track gradient (flat, downhill, or uphill).
* Braking percentage, indicated by the magnitude of braking force.
* Type of train (passenger/freight).
* Brake type (composite block/cast iron block).
* Weather conditions.
* Other technical factors.

Joni explained that train brakes operate using air pressure. The brake performance on the wheels is connected to pistons and cylinder assemblies. Reducing air pressure in the train forces the brakes to engage with the wheels.

Suddenly releasing the pressure, he said, would cause uneven braking, with the brakes engaging before the air is fully released.

“Uneven braking can cause the train or carriages to skid, derail, or even overturn,” Joni stated.

So, what is the average stopping distance for a train?

The following is a simulation based on the Surabaya Operational Area 8:

* At 120 km/h, the train stops after 800 meters.
* At 110 km/h, the train stops after 750 meters.
* At 100 km/h, the train stops after 505 meters.
* At 90 km/h, the train stops after 480 meters.
* At 80 km/h, the train stops after 379 meters.
* At 70 km/h, the train stops after 336 meters.
* At 60 km/h, the train stops after 221 meters.
* At 50 km/h, the train stops after 157 meters.
* At 45 km/h, the train stops after 132 meters.