Have you traveled by train and wondered why the train interior lights on passenger trains go on and off? Or when you arrive at a station, the train goes dark for a moment as you try to get off. This phenomenon happens not only on Amtrak trains but on commuter and light rail.
There is nothing wrong with the trains, and there is a very logical reason why this happens. Let’s find out what’s going on!
This article is not going into great technical detail because the average traveler does not need that much detail, but I want to let the average traveler know what is going on.
Interior lights go on and off to make trains more efficient
If you are at a station, the main reason for the lights to go on and off is efficiency.
Passenger locomotives produce power using Head End Power (HEP) for lights, heating and AC systems, outlets, and more, and it is called hotel power.
This system works well when traveling but is not as efficient when trains sit at stations for a long time.
The stations, where trains sit for a while, are often equipped with “house power.”
The train staff can “plug” the train in to use the station or house power instead of HEP.
This move can significantly save railroads money by saving fuel and reducing wear on equipment.
When trains switch from “house” to HEP or the other way around, the lights will go off in the car. That is why the lights go off.
Each car has a battery backup system to run emergency lights and the PA system. Ofen, this system engages for a few moments during the power swap.
A few things will not work during this time, like toilets and food cars.
Changes to the train during the route
A few times, the train may not power along the route.
If you ever travel through Washington DC on a long-distance train, you have experienced a long time where the power is off.
South of Washington DC, Amtrak uses diesel locomotives, and North of DC uses electric locomotives. In DC is where they make this swap out locomotives for the remainder of the journey. During this time, there will not be power on the train for the safety of the employees.
A few trains separate or come together en route, and like during equipment swaps; the train will not have power.
Safety checks and more power
Sometimes trains have to go through safety checks, and often during these tests, the engineers may need to turn off the power to the cars temporarily.
Sometimes locomotive engineers will turn off the HEP if the train needs more power. The HEP can reduce the power to the traction motors that power the train.
While you are traveling, the lights may go off.
If it is later at night and the light goes off, and they don’t come back on, it could be because it’s nighttime!
Amtrak will turn the lights off in coach cars at night so you can sleep.
Passenger cars transfer power from one to the next via cables; sometimes, these cables come undone during travel, which could cause the loss of electricity.
Once the train stops, the crew can reconnect the line, and all will be well.
What about interior lights on passenger rail with electric trains and locomotives?
There are two ways electric trains get their power, either overhead wires or a third rail.
An example of the third rail is Chicago’s CTA Subway/Elevated Lines. Each car makes contact with the third rail to get power for that car.
A train may lose power when going through a switch or crossing another track because the car lost contact with that power rail.
As soon as that car passes through that area, the power will come back on again.
Power loss on these trains can happen if the train loses contact with the overhead power.
Other reasons include going into a dead block. A “dead block” is when an overhead line does not have electricity, which could happen for various reasons.
I hope this answers your question on why interior lights on passenger trains go on and off.
On one journey to Chicago aboard a Metra train, the hotel power went off because a cable came loose. Since it was not dangerous, they waited till we arrived at the station to fix the problem since we were close.
It is fun to hear first-time train travelers gasp when it happens. You know that you can share this info with your travel companions.