Following a report from Comicbook.com http://comicbook.com/2014/09/14/was-the-punisher-being-established-in-captain-america-the-winter/ (the original link)
speculated through an interview from comingsoon.net that director of highly accailmed Marvel film The Winter Soldier the Russo brother reportedly hinted of future Marvel canon through establish a small but major scene where a truck collides to protect the heroes and destroys Hydra's vehicles "The man who drives that truck," Joe deadpans, joking that the driver is a candidate for a future Marvel One-Shot, "Is very highly trained. He thinks on his own terms. He's got a plan and a very specific skill set." Whilst this is only a speculation that it could be the deadly anti hero The Punisher who is a highly trained former agent, who fights for himself often killing and with plan of vengeance.
Maybe the driver could be another hero like Mockingbird
There are many other trained anti-heros but the one that sticks out is the Punisher as he has had a long standing relationship with Shield and as a result could have known about the events occurring with Hydra overtake of Shield, so its highly likely it was to be Punisher even though Mockingbird has a relationship with shield, her characteristics is far from crashing a truck into a herd of vehicles.
Captain America 3 releases on May 6 2016