when do chuck and blair get into a car accident
Riding in Town Cars with Boys Blair Waldorf (Leighton Meester): Blair does not hide her conflicted feelings as she comes to realize that there is a possible ending with Chuck in it and not Louis. She tries to stay away from going for Chuck, but she cannot help it. At the end of the episode, her and Chuck get in a car crash due to over-active paparazzi. She survives the crash.
Sarah Walker (Chuck) While on the run, Chuck and Sarah spend the night in a motel, and share a bed. While not under surveillance, they kiss and are close to having sex but are interrupted by a lack of a condom, followed by the appearance of Agent Casey. After Chuck successfully removes the Intersect from his head, Sarah is reassigned to work on the new Intersect project with Bryce, but soon decides not to go and instead stay with Chuck. But even after learning that she turned down the assignment, Chuck consciously re-establishes the professional barrier by uploading the new Intersect.