Sensors which detect whether a seat is free have been rolled out across an entire UK train fleet for the first time.
London North Eastern Railway (LNER) has begun using the technology above seats on all its trains to make it easier for passengers to avoid having to stand.
The system, which was first trialled in August, detects which seats are occupied by activating beam sensors twice between each station the train stops at.
Passengers can view digital maps showing which seats are free by connecting their smartphones to the onboard wi-fi.
A traffic light system has also been installed above seats to display their current and future availability.
This consists of:
- Green when a seat is unreserved for the whole journey
- Amber when a seat is reserved for part of the journey
- Red when a seat is reserved for the whole journey
LNER took over the operation of trains on the East Coast Main Line from Virgin Trains East Coast (VTEC) on June 24, returning the route to public ownership.
Labour leader Jeremy Corbyn was involved in a long-running row over seats with VTEC after recording a video in which he sat on the floor of a London to Newcastle train in August 2016.
Mr Corbyn claimed the service was "ram-packed" but VTEC insisted he and his team walked past available seats before filming started.
LNER commercial director Suzanne Donnelly said: "We know some of our customers can become anxious when they are trying to find a seat, whether they are asking for their reserved seat back from another passenger or struggling to find an available unreserved space.
"The innovative seat sensor technology addresses this by making it much easier for all of our customers to find a seat. We hope this improves their overall journey experience."