你的判断是正确的。

merge with 意为“与…结合，联合，合并”。

merge with traffic 意为“融入车流中”。

Check your mirrors and look over your shoulder to check your blind spot until you can merge safely with traffic. 通过后视镜观察后方路况，以及查看盲点，直至安全并入高速车流。

When merging with traffic on the main road, the driver should turn on the turn signal in advance and observe carefully. 驾驶车辆汇入主干道车流时，应提前开启转向灯，并仔细观察。