Using one pedal to control speed means that it's ridiculously easy to gradually and almost imperceptibly slow down (Teslas don't coast like other cars—if you're not speeding up, you're slowing down).

Of course, they eventually look up, realize that they're going 7 under in the fast lane, and blaze through the intersection at 10 over, right as it goes from yellow to red—just in time for them, just a bit too late for you...