On Taobao/Tmall,
直通车 is the keyword-bidding ad system — sellers bid on search terms and pay per click, like Google AdWords for Chinese e-commerce. Verb
开直通车 = 'to run a Through Train campaign.' The platform borrowed the name from the literal sense: a
直通 train going straight to a destination without stops. CC-CEDICT also notes the historical Hong Kong/Macao political sense ('through-train' legislators retained across the handover), now rare.
