Have you traveled by train and wondered why passenger train lights 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 on Amtrak and commuter trains, and light rail.
There is nothing wrong with the trains and a logical reason for this. 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. Still, I want to let the average traveler know what is happening.
Interior lights go on and off to make trains more efficient
If you are at a station, efficiency is the main reason the lights go on and off.
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. Often, 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.
Equipment swap
If you ever travel through Washington DC on a long-distance train, you have experienced a long time when the power is off.
South of Washington DC, Amtrak uses diesel locomotives, and North of DC uses electric locomotives.
In DC, is where Amtrak does the engine swap. During this time, there will not be power on the train for the safety of the employees.
Combing trains
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 during these tests, the engineers may need to temporarily turn off the car’s power.
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 contacts 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 loses contact with that power rail.
The power will return as soon as that car passes through that area.
Other electric trains use overhead wires; examples include the South Shore Line, Amtrak’s Northeast Corridor, and streetcars in San Fransisco.
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.
Wrap-up
I hope this answers your question about 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 became loose and disconnected. 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.
Safe travels!
Kev
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