What are the advantages and disadvantages of self-driving cars?

Vehicles that can coordinate use road space better than ones that cannot

Question: What are the advantages and disadvantages of self-driving cars?
Position1 of 2›: Advantages of self-driving cars include less traffic, and fewer accidents
Argument‹2 of 2: Vehicles that can coordinate use road space better than ones that cannot

The argument

The second advantage claimed concerns congestion. Proponents argue that much everyday traffic is caused not by too many vehicles for the road but by how people behave in dense conditions. Drivers leave inconsistent gaps, brake harder than necessary and react to the lights ahead of them with a delay, which amplifies each small disturbance into a wave travelling backwards along the queue. Jams of this kind appear with no collision and no obstruction, purely from the dynamics of human reaction. Automated vehicles, on this account, remove the mechanism. A system can hold a steady gap, accelerate and brake smoothly, and respond to a disturbance without the delay that amplifies it, so the wave is damped rather than reinforced. Where vehicles can exchange information, they can act on what is happening further ahead than any driver can see, adjusting speed before a disturbance reaches them and clearing junctions in sequence rather than in competition. Proponents argue that the secondary effects follow from the same capacity. Smoother flow means fewer stops, and so less fuel and less wear. Vehicles that can be summoned, and that need not wait for their owner, can be shared, which takes parked cars off the kerb and land out of car parks. Journeys currently unavailable to people who cannot drive, whether through age, disability or cost, become available. On this account the advantage is not that each vehicle is cleverer but that the traffic as a whole behaves as a system rather than as a crowd.

Premises

[P1]Much congestion arises not from the number of vehicles but from how people drive in dense traffic, leaving inconsistent gaps and braking late and hard. [P2] Those behaviours amplify small disturbances into waves that travel backwards along a queue, which is why jams appear with no collision or obstruction. [P3] An automated vehicle can hold a steady gap, respond without the delay that amplifies a disturbance, and act on information from further ahead than a driver can see. [C] Therefore less traffic is an advantage of self-driving cars.

Counter-arguments

Critics answer that the benefit depends on a road full of automated vehicles and largely disappears on a mixed road, which is the condition that would hold for a long time. A handful of smooth vehicles among human drivers is absorbed by the behaviour around them, and drivers tend to exploit anything that leaves a consistent gap. They add that easier travel generates more of it: if journeys become cheaper, more comfortable and available to people who cannot currently drive, more journeys will be made, and the capacity saved by smoother flow is consumed by the extra demand. On that view the congestion advantage is clear in a simulation and uncertain on a street.

Rejecting the premises

[Rejecting P1] Congestion also arises straightforwardly from demand exceeding capacity, which smoother driving does nothing to address. [Rejecting P2] Damping those waves requires most of the traffic to be automated, so the premise describes a benefit that a long mixed period would postpone. [Rejecting P3] Vehicles that keep consistent gaps are exploited by human drivers merging into them, which reintroduces the disturbance the premise removes. [Rejecting C] At most it follows that automated traffic flows more smoothly in itself, not that total traffic falls, since cheaper and easier journeys induce more of them.