Reliability

An engine statistic in percent, listed for every engine; research upgrades raise it, like speed and acceleration.

Reliability is an engine statistic, in percent, given for every engine.

Research upgrades raise it, along with speed and acceleration.
Engine upgrades bought for gold can also raise it: +25% for the Titan and the Aurore, the endgame bonus engines.
A train in poor condition runs slower: service your trains. A mechanic voucher restores a damaged engine to perfect condition.