Electric cars are here, and are already having a significant impact on the roads. But they still have a problem with range. The small ones: the Leaf, the BMW i3, etc., have a range which is fine for the typical daily commute, and even for a lot of delivery services. But recharging in most cases can only be done at 20 miles of range per hour. But for occasional longer trips, they remain a problem, and you have to spend several hours on the charger for every hour you drive. Not adequate if you're taking a trip that's substantially longer than the range of the battery. So far, Tesla has the most complete solution: 1) a much bigger battery than the others, giving 250+ miles of range. 2) faster "destination" charging, as much as 60 miles of range per hour, so you can put those 250 miles of range on in only 4 or so hours, allowing two or three cars to use the same charger over the course of a night, and finally, the Tesla "supercharger", which can put 150 miles of range on 20 minutes. Presently, these are located about 150 miles apart on most of the big cross country routes in the US, but there are still a lot of gaps. Tesla has promised to get around to them, but it'll be a while.
The second best solution is to make some sort of fuel-electric hybrid. there are a number of plug-in hybrids available, but all have a very short range. If your commute is very short and you're careful to plug in every night, it may work for you, but for long range travel, you're just a relatively efficient internal combustion engine car.
My idea is to put power rails along the roadway. Whether these have inductive pickup or are actual physical rollers that run on rails is an engineering decision. I'd put these on the interstates--the same routes where Tesla is putting its superchargers--and reserve a lane for them. The new Teslas come with the ability hold lane, speed and following distance on their own (although lane following is still in alpha), and this is all it would take to have the car drive itself on an accurately delineated charger lane. Many other carmakers have similar features available. There is no particular reason that following distances couldn't be short and speeds high, as long as the computer is doing the driving. The car will arrive at its destination city fully charged, and the driver rested.
The Tesla Model S charging at 19.2KW, charges at 60 miles of rated range per hour, so this is what it would need to maintain steady charge state at 60 mph at the rated characteristics. This is probably all that's necessary. The car draws less than that while going straight and level, but more accelerating or going uphill. The battery can handle surges--the power rail is just for topping up. It needs to be arranged so that all the cars needing to be charged can have their own charger. Simplest would be for each car to tap into the same (say) 600VDC rail pair simultaneously and regulate itself so it never draws enough power to cause the voltage to drop more than a small amount. If more power is needed, it reduces its charge rate and draws from its own battery.
Issues:
The power rails would probably need their own substation few miles or so. Highly loaded, this would be 50 cars per mile or so. 19.2*50=960... a megawatt. Those big, 200+ foot wind turbines put out 1.5 to 3 MW at their peak, so having one every mile or so would work nicely when the wind is blowing. A strip of solar panels along the road 6 meters wide (20 ft) would do the same thing when the sun is shining. (there's a company that's trying to sell solar panels that work AS road surface...I think you could make this work by paving the special lane with such things)
If the power available is exceeded, the cars can run on their batteries, but they should probably be aware of what's happening. If it's a traffic jam, they'd probably need to slow down and this will automatically reduce the power drawn.
600VDC with the availability to deliver 1600 amps would cause major badness to occur to any conductor that happened to fall across it, including a person or animal. the conductors either need to be protected somehow, or buried with inductive pickup.
there should probably be some mechanism to keep non-robodriven cars out of the special lane. I think the double white lines and reflective bumps as used on toll lanes, are not quite enough. There is no real safety problem with illegal use of a toll lane. There is with power rails and high-speed robocars,
billing should be straightforward. the car would have a tamper-resistant meter which monitors the number, location and timing of watt/hr picked up and communicate it with substation, which would bill appropriately, and prevent incorrectly equipped cars from driving on the road. If it becomes a problem, substation can monitor load and correlate it with the traffic data to detect tampering. I suspect it won't be...once the roadside infrastructure is built, it'll last for decades and cost very little to maintain. It'll pay itself off in a few years.
heavy trucks should be able to use this. they'll obviously draw more power. the road design can handle this straightforwardly. more megawatts per mile.
because all the cars are robodriven, including the heavy trucks, all the vehicles will run down exactly the same part of the road, and rutting will be a worse problem than it will be on roads with human drivers. Since there's a parallel road and all the vehicles have batteries, repairing it will be pretty much the same as with present roads.
