Track and wayside detectors

BNSF uses a range of sophisticated detection equipment on its network to keep trains operating safely.

A railroad track consists of steel rails, ties and ballast. The ties hold the rails in position; in the U.S. the gauge, or distance between the rails, is 56.5 inches. Most BNSF ties are wood, but concrete ties are also used.

The rails are restrained from moving by anchors on wood ties and elastic clips on concrete ties. If they weren't restrained, a 100-degree temperature change in the rails (a common occurrence over the course of a year) could cause the network to grow or shrink up to 25 miles due to expansion and contraction.

BNSF uses ballast made up of crushed rock to keep the track structure stable and well drained.

Wayside detectors

Hot bearing detectors like the one pictured here monitor wheel bearing temperatures as a train passes by. This prevents overheating, which could lead to derailments.

The device pictured uses infrared, which allows for measurement of temperatures from a trackside device several inches away from the train. We also use other types of detectors. Truck performance detectors use lasers to measure the alignment of wheel plates with the rail. Wheel impact detectors check the structural condition of the wheels.

When a problem is detected, the device transmits the information to personnel who can order the train to stop or proceed to a maintenance yard if necessary.


A block signal stands guard at the entrance to a block, or section of track. The indication on the signal governs when trains can enter and use the block. If a portion of a train is anywhere within the block, the signal light will be red, requiring any approaching train to stop. BNSF has almost 25,000 signals on its network.

Oversized loads

BNSF is able to haul "dimensional" items of unusual size and shape. For instance, BNSF has been moving a significant number of wind energy products, the massive components that make up wind turbines - blades, nacelles and towers.

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