Understanding the Need for Heat Restrictions
Steel rails slowly expand and contract as temperatures rise and fall. With a substantial change in temperature, even in early March, there can be heat restrictions.
During summer riders may experience heat restrictions on the Fredericksburg Line from 1-7 p.m. For the uninitiated, heat related delays accumulate over the course of the trip so the farther you go, the longer the delay will be.
If your destination is Franconia-Springfield, you will likely not notice the two minute delay. However, if you travel all the way to Fredericksburg, the delay will be approximately eleven minutes. The train crews will do everything they can to make up time along the way to minimize any delays. Just as automobiles are sometimes requested to lower speeds for various road and weather conditions, trains are subject to similar restrictions. Heat restrictions are orders given to railroad engineers to reduce their speed over a given section of track.
Steel rails slowly expand and contract as temperatures rise and fall. With a substantial change in temperature, even in early March, there can be heat restrictions. Careful engineering measures are taken when rail is installed to account for rail expansion and contraction. The ties, rock ballast, and rail anchors, which hold the rail longitudinally, must be strong enough to keep the rail solidly in place instead of expanding or contracting. Under extreme heat, the rail, on rare occasions, will experience a "sun kink", which causes the track to shift laterally causing a curve in the track.
When a "kink" or high tension is found in the track, the track is taken out of service, repaired, and then put back in service. That is why there are times that we are limited to one track during the summer as repairs are made.