The general critique made by Schnaars in Megamistakes (that I discussed here) applies to driverless car technology: consumers may be unwilling to pay the added cost despite the safety benefits.

I don't see added costs. Driverless cars will compete with cabs. Google driverless car model is supposed to be a two seater. It will need less fuel than the average four seater cab and it won't have to transport a paid cab driver.

(a) the date that the first commercial driverless car will hit the market in a major country or US state?

Does a car being for rent mean that the car is on the market?

(b) the date by which over 10% of new cars sold in a large country or US state will be driverless (i.e., capable of fully autonomous operation)

I don't think that the majority of cars will be brought by end consumers so I'm not quite sure what you mean with sold.

(d) the date by which over 10% of cars on the road (in a large country or US state)

Is a car that's parking a car that's on the road? Are we talking about rush hour or are we talking about 1 AM?

What's your overall view on whether it is desirable at the margin to speed up or slow down the arrival of autonomous vehicles on the road? What factors would you consider in answering such a question?

Speed up. Driveless cabs are very useful for many reasons. As they are book per use you drive a 2 seater instead of a 4 seater if you go with 1-2 people from place A to B. Smart cars can reduce the distance to each other so they can drive in slipstream of each other. The driverless cab company has huge incentives to reduce energy usage of the cars and make them as fuel efficient as possible.

Without private car ownership you don't need to waste so much city real estate with parking spaces.