3s is a good rule of thumb for highway. Iirc the CDL manual for my state said 1 second for a 20ft vehicle below 45mph, then add a second if it’s above 45mph. Also add a second for every 20ft of vehicle length above 20ft.
Also add 1-2 seconds if the vehicle on front is a motorcycle, since they can stop on a dime
3s is a good rule of thumb for highway. Iirc the CDL manual for my state said 1 second for a 20ft vehicle below 45mph, then add a second if it’s above 45mph. Also add a second for every 20ft of vehicle length above 20ft.
Also add 1-2 seconds if the vehicle on front is a motorcycle, since they can stop on a dime