  The introduction of autonomous vehicles (AVs) will have far-reaching effects
on road traffic in cities and on highways.The implementation of automated
highway system (AHS), possibly with a dedicated lane only for AVs, is believed
to be a requirement to maximise the benefit from the advantages of AVs. We
study the ramifications of an increasing percentage of AVs on the traffic
system with and without the introduction of a dedicated AV lane on highways. We
conduct an analytical evaluation of a simplified scenario and a macroscopic
simulation of the city of Singapore under user equilibrium conditions with a
realistic traffic demand. We present findings regarding average travel time,
fuel consumption, throughput and road usage. Instead of only considering the
highways, we also focus on the effects on the remaining road network. Our
results show a reduction of average travel time and fuel consumption as a
result of increasing the portion of AVs in the system. We show that the
introduction of an AV lane is not beneficial in terms of average commute time.
Examining the effects of the AV population only, however, the AV lane provides
a considerable reduction of travel time (approx. 25%) at the price of delaying
conventional vehicles (approx. 7%). Furthermore a notable shift of travel
demand away from the highways towards major and small roads is noticed in early
stages of AV penetration of the system. Finally, our findings show that after a
certain threshold percentage of AVs the differences between AV and no AV lane
scenarios become negligible.
