"I looked down at my Polar HRM with wireless speedometer and odometer and saw that I was allegedly going 68 mph!"
This probably explains how my computer mysteriously registered a 73 MPH maximum speed when I got to work the other day. I only have 2 signals that are regularly red & there is enough traffic most days to trip them. The few times I'm alone, I just have to stand with my bike at a slight angle to trip them.