Traffic
Additional advantages could include higher speed limits; smoother rides;
and increased roadway capacity; and minimized traffic congestion, due to
decreased need for safety gaps and higher speeds. Currently, maximum
controlled-access highway throughput or capacity according to the U.S.
Highway Capacity Manual is about 2,200 passenger vehicles per hour per
lane, with about 5% of the available road space is taken up by cars.
One study estimated that automated cars could increase capacity by 273%
(~8,200 cars per hour per lane). The study also
estimated that with 100% connected vehicles using vehicle-to-vehicle
communication, capacity could reach 12,000 passenger vehicles per hour
(up 445% from 2,200 pc/h per lane) traveling safely at 120 km/h (75
mph) with a following gap of about 6 m (20 ft) of each other. Currently,
at highway speeds drivers keep between 40 to 50 m (130 to 160 ft) away
from the car in front. These increases in highway capacity could have a
significant impact in traffic congestion, particularly in urban areas,
and even effectively end highway congestion in some places. The ability
for authorities to manage traffic flow would increase, given the extra
data and driving behavior predictability combined with less need for
traffic police and even road signage.