# Electric Trains on Hot Days **URL:** \ **Category:** Factual Questions\ **Created:** [July 1, 2025, 2:37am UTC](https://boards.straightdope.com/t/electric-trains-on-hot-days/1020329 "2025-07-01T02:37:40Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [July 1, 2025, 2:37am UTC](https://boards.straightdope.com/t/electric-trains-on-hot-days/1020329/1 "2025-07-01T02:37:40Z")
Why do electrified trains have to obey a slower speed limit on hot days? I always thought it is because the overhead wires expand and droop more (from catenary action). Thus, the pantograph is more likely to snap a wire. Or, is it because the track expands and a derailment is more likely at higher speed? Or, other? Please explain. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [July 1, 2025, 3:01am UTC](https://boards.straightdope.com/t/electric-trains-on-hot-days/1020329/2 "2025-07-01T03:01:20Z")
> **[Why Extreme Heat Causes Amtrak Delays](https://time.com/6990849/extreme-heat-amtrak-delays/#:~:text=Extreme%20heat%20can,adjust%20course%20accordingly:)** > > The “heat dome” that has affected more than a hundred million Americans is causing some minor delays for Amtrak trains. > _Extreme heat can affect Amtrak infrastructure. For instance, if tracks get too hot, they can develop a kink; or if overhead power wires—called a catenary system—get too hot, they can sag, Anderson shares. When the temperature of the rails reaches a certain threshold, Amtrak requires that locomotive engineers operate trains at slower speeds than usual, in order to spot potential hazards and adjust course accordingly._ Stranger ---
**Author:** ![Broomstick](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/broomstick/32/246_2.png) [@Broomstick](https://boards.straightdope.com/u/Broomstick)\ **Post date:** [July 1, 2025, 3:25am UTC](https://boards.straightdope.com/t/electric-trains-on-hot-days/1020329/3 "2025-07-01T03:25:11Z")
> [@Jinx](#): > > Thus, the pantograph is more likely to snap a wire. Or, is it because the track expands and a derailment is more likely at higher speed? A little of both I’d say. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [July 1, 2025, 2:21pm UTC](https://boards.straightdope.com/t/electric-trains-on-hot-days/1020329/4 "2025-07-01T14:21:30Z")
I know what the Amtrak spokesperson meant, but saying that a railroad engineer will “spot hazards and adjust course” sounds so wrong. Not much swerving in the railroad biz. ---
**Author:** ![Marvin\_the\_Martian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/marvin_the_martian/32/2898_2.png) [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)\ **Post date:** [July 1, 2025, 3:10pm UTC](https://boards.straightdope.com/t/electric-trains-on-hot-days/1020329/5 "2025-07-01T15:10:05Z")
> [@LSLGuy](#): > > Not much swerving in the railroad biz. Reminds me of one of my favorite books from childhood. “Stay on the track no matter what!” [![](https://upload.wikimedia.org/wikipedia/en/thumb/c/c7/Tootle.jpg/250px-Tootle.jpg) ](https://upload.wikimedia.org/wikipedia/en/thumb/c/c7/Tootle.jpg/250px-Tootle.jpg) ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [July 1, 2025, 3:36pm UTC](https://boards.straightdope.com/t/electric-trains-on-hot-days/1020329/6 "2025-07-01T15:36:39Z")
I probably had that book too. So cute. In railroad-speak, a derailment is “train on the ground”. Which also strikes me funny. They neither fly nor float, so where else would they be? But “on the ground” of course is different from “on the tracks” where they do belong. ---
**Author:** ![Q.Q.Switcheroo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/q.q.switcheroo/32/5713_2.png) [@Q.Q.Switcheroo](https://boards.straightdope.com/u/Q.Q.Switcheroo)\ **Post date:** [July 1, 2025, 3:44pm UTC](https://boards.straightdope.com/t/electric-trains-on-hot-days/1020329/7 "2025-07-01T15:44:27Z")
> [@Stranger\_On\_A\_Train](#): > > _if tracks get too hot, they can develop a kink_ “Phrasing!” ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [July 1, 2025, 11:26pm UTC](https://boards.straightdope.com/t/electric-trains-on-hot-days/1020329/8 "2025-07-01T23:26:57Z")
I’ve been on trains that had to go slow because it was too hot and the track might buckle (it was diesel, no catenary) and on at least one that had to go slow because it was too cold and the track might crack. On one cold day, the train was not allowed north of Albany and we were bussed. I think a lot of this is due to poor quality rails. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [July 2, 2025, 12:45am UTC](https://boards.straightdope.com/t/electric-trains-on-hot-days/1020329/9 "2025-07-02T00:45:07Z")
Or a management decision to accept slow running and failures on some small _x_ number of days per year rather than WAG doubling the cost of trackage built to operate healthily at any temp between e.g. -60C and +60C. ---
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [July 2, 2025, 1:13am UTC](https://boards.straightdope.com/t/electric-trains-on-hot-days/1020329/10 "2025-07-02T01:13:12Z")
Bingo! Thanks! ---
**Author:** ![Kedikat](https://avatars.discourse-cdn.com/v4/letter/k/ed655f/32.png) [@Kedikat](https://boards.straightdope.com/u/Kedikat)\ **Post date:** [July 2, 2025, 2:58am UTC](https://boards.straightdope.com/t/electric-trains-on-hot-days/1020329/11 "2025-07-02T02:58:14Z")
Surprised they don’t have some sort of temperature expansion/contraction device to counter the droop of the power cables. For rails it might be too difficult or impractical. ---
**Author:** ![kferr](https://avatars.discourse-cdn.com/v4/letter/k/71e660/32.png) [@kferr](https://boards.straightdope.com/u/kferr)\ **Post date:** [July 2, 2025, 12:08pm UTC](https://boards.straightdope.com/t/electric-trains-on-hot-days/1020329/12 "2025-07-02T12:08:51Z")
In the UK I see line tensioners like this: [![](https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Ftse1.mm.bing.net%2Fth%2Fid%2FOIP.08893p1TM7O2vYa26tm9SgHaLu%3Fpid%3DApi&f=1&ipt=5fe241489b668cb33bd2dfcfe4a5e4ce8fa6f4c0ef7f4fa141e5359a5f078283&ipo=images) ](https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Ftse1.mm.bing.net%2Fth%2Fid%2FOIP.08893p1TM7O2vYa26tm9SgHaLu%3Fpid%3DApi&f=1&ipt=5fe241489b668cb33bd2dfcfe4a5e4ce8fa6f4c0ef7f4fa141e5359a5f078283&ipo=images) ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [July 2, 2025, 1:02pm UTC](https://boards.straightdope.com/t/electric-trains-on-hot-days/1020329/13 "2025-07-02T13:02:17Z")
A lot of the catenary on the northeast corridor between New York City and Washington DC was installed in the 1930s, and hasn’t been upgraded since, so the tensioning system is rudimentary at best. North of NYC there’s newer stuff, and some other sections were replaced/upgraded, but overall it’s pretty outdated. ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [July 15, 2025, 2:54am UTC](https://boards.straightdope.com/t/electric-trains-on-hot-days/1020329/14 "2025-07-15T02:54:34Z")
> [@Stranger\_On\_A\_Train](#): > > at slower speeds than usual, in order to spot potential hazards In the UK, they used to run a pilot / scout engine up the tracks before the mail express, so that the mail express could run full speed in winter. ---
**Author:** ![MikeF](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@MikeF](https://boards.straightdope.com/u/MikeF)\ **Post date:** [July 19, 2025, 11:41am UTC](https://boards.straightdope.com/t/electric-trains-on-hot-days/1020329/15 "2025-07-19T11:41:37Z")
“Course” of action? ---
**Author:** ![Coriolanus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/coriolanus/32/18769_2.png) [@Coriolanus](https://boards.straightdope.com/u/Coriolanus)\ **Post date:** [July 23, 2025, 11:45pm UTC](https://boards.straightdope.com/t/electric-trains-on-hot-days/1020329/16 "2025-07-23T23:45:15Z")
I do not believe it was the rails, yet I was at a station Woking (24C) in the UK where they announced lots of trains from Reading and/or to Salisbury were cancelled because there were too many out of service.