DataDan
Mama says he's bona fide
This is a dangerous underestimation. At +20mph, vehicles within 50ft (about 3 car lengths) are an immediate threat. If a vehicle 2 car-lengths ahead suddenly changes lanes, you're going to hit it. Probably not very hard, and if you go down, you probably won't be seriously injured. But you won't be able to prevent the collision.What are the general recommendations for deltas when:
1. cars completely stoped
2. cars barely moving 10-20mph
3. cars moving less than speed limit 20-60
I caught myself doing a over 30 mph yesterday when cars were completely stopped on the highway. My brain didn't register it as being dangerous but once I saw the 30+ delta I slowed down a little. Generally try to stick to <20mph delta since 20 mph can be scrubbed off near instantly.
My estimate assumes 1 second reaction and 16ft/s^2 deceleration (MSF-level braking skill--I don't know what the TCT standard is).