you have 2 options,
a) withou exceeding the speed limit, you get a PROPER DISTANCE ahead of the vehical on the highway
b) you pace yourself to fall in a PROPER DISTANCE behind the vehical already on the highway
its just like an intersection on a surface street, its the full responsibility of the turning vehical to do a proper turn. weather its a 90 degree turn or simply moving over a lane
its up to the driver thats going straight if he / she WANTS to speed up, slow down, or move over