While the full benefit of robocar technology comes when they drive passengers around, a great deal of that benefit might come earlier through what I've called a "Whistlecar." This is a car which people still drive, but which is permitted to move around streets while vacant, so that it can deliver itself to drivers, as well as park and refuel itself. I call it a whistlecar because it may remind you of the Lone Ranger's ability to just whistle and have his steed come to him to ride.
This becomes important if whistlecars can be deployed considerably sooner than full robocars. That early deployment could not only provide many benefits, it will also provide a demonstration that encourages the adoption of robocar technology.
While vehicles are unoccupied, many of the constraints change. In particular, it is no longer necessary to be trusted as safe enough to carry passengers. The vehicles must still be safe enough not to harm pedestrians, property or other vehicles, but this is a less difficult standard.
One reason it's easier is that unoccupied vehicles don't have to drive quickly enough to please their impatient occupants. Nor do they need to be able to drive on all roads. Their main need for speed will come from impatient drivers waiting for a car, and people stuck behind a slower vehicle.
On the other hand, an empty car can't make use of the resources of a local human to get it through situations the software can't handle.
At slower speed, it is easier to be safe. In particular, below about 20 mph, a vehicle can use shorter-range sensing technologies like LIDAR to detect things and still be able to full stop, if necessary. And quite simply, at lower speeds, even accidents can't do as much damage, and that damage can be mitigated by things like airbags -- on the outside of the vehicle as well as the inside. Not that we would expect whistlecars to be hitting things with any frequency approaching how often human driven cars do, but people could be made more comfortable by such saftey systems.
Whistlecars could avoid roads with heavy or high-speed traffic. If traffic got too difficult for their safety rules, they could pull over temporarily or move to alternate routes. Indeed, some roads could be off-limits to whistlecars unless they are delivering themselves to a driver on that road. Whistlecars might never go on the highway without a driver.
It's also possible that whistlecars could require special roads, with special lane markings or magnetic markers, before they could move at reasonable speed. They still need to be able to go on any road to deliver themselves to the driver, but that last small section could be done at a slower, safer speed. There could even be special lanes for whistlecars, and if they are all small and light, there could be dedicted tunnels or low-cost overhead guideways.
Whistlecars need not be as smart as robocars in dealing with confusing situations. For example, a whistlecar might operate in "televalet" mode where a high speed data network allows a human being to see views in all directions and operate the car when the car detects something it can't figure out. In such situations, the car would move slowly (or stop if need be) in a safe mode until a televalet was available to resolve the problem. A staff of televalets would sit in special driving chairs, switching from car to car, solving problems only humans can solve. Among those problems might be driving that last mile to a driver on roads not rated for whistlecar autonomous operation. If the data network were to fail, the whistlecar would move to a slow or stopped safe state until it was restored.
All of these techniques might generate acceptance of whistlecars years before the public is ready to accept full robocars moving on roads at acceptable speeds.
Driven by humans, whistlecars themselves would not save us from the accidents and traffic congestion caused by human drivers. However, the same technology that lets them drive slowly and detect problems would make a highly accident-resistent car, even with a person behind the wheel. Many potential accidents would be avoided thanks to the ever-vigilant, 360-degree watchful eyes of the whistlecar control systems.
With whistlecars, we make car-sharing a workable proposition for many people. Today, car-sharing is used by only a small minority, because its restrictions are quite cumbersome. One must go to a car sharing lot to get your car, and that lot may be some walk away. A car of the type you want -- or any car -- may not be available.
The same must be done on your return: If you want to bring some shopping home you must first drive home, unload, and then drive to the car-share lot and get back from it. Generally, one-way rentals are not permitted, so you must pay for the car while you park it at your destination, and you have to bring it back home, on your dime.
Whistlecar car-sharing will be very pleasant. Arrange a car in advance, or hail it from your cell phone. It's waiting in your driveway at the appointed time. It's the right car for your trip -- quite often a single-seat short-range electric car which is super-cheap to operate. Drive it where you want to go, and get out. It will worry about its next rental, and it will worry about refueling itself.
(One-way rental may not always be possible at peak-demand times if it's not practical for the cars to return on a long trek on their own.)
As noted, you would be able to call up both a single person whistlecar, or a larger one when you need it. This provides a similar "right car" solution as robocars do. This right car approach means a drastic drop in the energy needs of transportation. It also means that people can own a car that meets only most of their needs, and whistle up a special car when they need it. If they need an SUV, minivan or pickup truck, they can have that for those few trips, and stick to a much more efficient car for everyday use.
Just like robocars, whistlecars would make themselves to refueling stations for recharge, battery swap or new experimental fuels. Just like robocars, they solve the infrastructure problems associated with different forms of power.
These features combine to allow the common use of small, lightweight single person whistlecars that run on batteries and only have a short range. Such vehicles are 10 times more efficient than cars or most U.S. transit systems and thus produce a very green result for the urban portion of our driving.
In addition, if there are other types of whistlecars available, many people may elect to not own a car, but always hire one or share one, significantly reducing the energy spent on car manufacture.
Note that self-refueling also allows, as robocars do, for the use of experimental fuels where the stations are not very conveniently located. People demand that gas stations be very common and convenient to their travels, won't care where the refueling stations for whistlecars are. This solves the chicken-and-egg problem on fuel stations for new types of fuel.
Whistlecars will of course be able to park themselves. They should be able to gain almost all the benefits of robocars when it comes to parking. Their reduced speed will simply mean they can't get quite as far away from their owner and still reach her as quickly, but this is not a major concern.
The whistlecar and deliverbot are roughly the same technology, except the deliverbot never carries anything but cargo and so doesn't need passenger safety systems, like air bags or crumple zones. However, many of the benefits of deliverbots -- including the ability to use one when you need to move cargo rather than having to own or rent a truck -- will come at the same time as the whistlecar.
In general, the whistlecars should offer almost all the advantage of robocars, with these key exceptions: