Giving directions to a place in Houston does you no good if you're in the middle of San Antonio. Direction matters but so do current positions.
You can make great time going west on I-10 but if you're in San Antonio, don't expect to see Houston for some time. Of course, going west from Beaumont is a great idea if your destination is Houston.
What I'm saying is before you tell someone to take an offramp, find out where they are.