It's not just courteous, it's self serving, AFAIK, a self-emergent phenomenon. If you're driving at 65 mph and anticipate a slow down in your lane due merging t

It's not just courteous, it's self serving, AFAIK, a self-emergent phenomenon. If you're driving at 65 mph and anticipate a slow down in your lane due merging traffic, do you stay in your lane and slow down to 40 mph, or do you change lanes (if it's safe to do so) and maintain your speed? Texas highways allow for much higher merging speeds at the cost of far large (land area), 5-level interchanges rather than 35 mph offramps and onramps common in California. Any defensive driving course (which fall under instruction IMO) states that you don't always have to exercise your right of way, and indeed it may be unsafe to do so in some circumstances. Anticipating the actions of other drivers around you and avoiding potentially dangerous are the other aspects of being a defensive driver, and those concepts are consistent with freeing up the lane slower-moving vehicles are merging onto when it's safe to do so.