• Seat belt detection frequency – The percentage of miles driven while the seat belt was
fastened for each occupied seating position.
• Passenger presence detection – The percent of miles driven when the PPD sensors were
triggered. Each seat position was reported separately.
• Speeding exceedance – The percentage of miles the vehicle was driven at speeds greater
than the speed limit within each of four speed bins (i.e., between 1 and 5 mph greater
than the speed limit, between 6 and 10 mph greater than the speed limit; between 11 and
15 mph greater than the speed limit, and greater than 15 mph greater than the speed
limit). SE was only available for road segments represented within the NAVTEQ
database with a speed limit. Speed data for road segments without a precise speed limit
were excluded from this measure.
• G-force threshold exceedance (G) – Positive (left) and negative (right) lateral
accelerations as well as positive (acceleration) and negative (deceleration) longitudinal
accelerations were recorded. The percentage of miles the vehicle was driven within each
of four bins of acceleration (i.e., between 2 m/s2 and 3 m/s2
, between 3 m/s2 and 4 m/s2
,
between 4 m/s2 and 5 m/s2
, and in exceedance of 5 m/s2
). For reference, 1 G is equal to
9.82 m/s2
.
• System warning count – For each stage (i.e., baseline, each of three treatment stages, and
the transfer stage) a count was established to identify the issue of a warning. For each
subsystem, the count was summed and then divided by the total miles traveled as a
measure of the warning frequency per mile.