Elon Musk has bragged that soon the "Summon" mode in Teslas will let you summon the car from across the country. They are a very long way from that, but there is a summoning application which they could implement which would actually be useful and solve a problem electric cars have, namely the sharing of charging stations -- particularly the supercharger.

Valet parking was one of the earliest robocar demonstrations. I first proposed it 10 years ago and Stanford and Audi did demos. It was actually the very first Cruise business plan. Except for the issue of pedestrians in the lot, it's one of the easiest problems to solve, and it can be done with just cameras because it's all low speed.

With low speed chargers, the problem is cars park there for hours, sometimes all day, and stay there after they are full. Some charging stations toss on a low charge like $2/hour to hog the station, but if you parked some distance from your destination, that's not much of a solution.

With the superchargers, there are two problems. Sometimes the superchargers are all full, and people sit in their car waiting. Once the supercharging is done, Tesla charges you a large fee to hog the station, unless you come get your car within 5 minutes.

The cars should be able to park in charging spots, and leave them for regular spots, but they can't plug themselves in or remove the plug. The answer is to get the arrivals and departures to be the plug jockeys, by not letting them charge unless they have done a quick round plugging and unplugging the cars that need it. Frankly, most people would probably do that as a courtesy anyway, if asked.

Here's how it could work.

1. When you arrive at the charging lot, take an empty space, or if there are none, park in a marked regular "waiting" space near the chargers. The system might allocate a space for you, even reserve you one. If somebody is in the space, just tell it and you'll get assigned another.
2. The screen of your car, and the app in your phone, will present you with the list of cars that need plugging or unplugging. In addition, LEDs on the charging stations could in future indicate this status. Walk around the lot attending to the cars, and of course plug in your car if you got a free charging station.
3. All cars in the lot are scanning the lot for pedestrians and other cars. They indicate to the Tesla server when the lot is clear, and the Tesla server tells the cars that need to move that this is true, one at a time.
4. If a car is waiting for spot, and one is finished and unplugged, they switch places. (One car would drive just past the other, then wait for it to pull out, and back in.)
5. Otherwise, as needed, cars move to free spots when available, and out of spots to waiting spots once unplugged.
6. When a human arrives to pick up their car, they must do a quick run, as specified on their app and car screen, to plug and unplug cars. If they don't, they are not blocked from leaving but they pay a penalty.

As designed, the cars never move on their own if there is another car or pedestrian in the charging area. This presents a problem if somebody enters the area during car movement. The cars could be flashing a special light pattern to indicate they are in valet movement mode which people would come to learn. Or they could stop dead if a pedestrian arrives. Ideally the lots would have sidewalks to let people get to the charging stalls without walking in the driving area.

This approach designates a set of regular parking stalls as waiting zones. In some lots that's easy, in others it's harder, or might be some distance from the charging area. To handle the latter, the cars would need to be rated for safe movement with pedestrians. The first version of this is designed to be done with just a software upgrade. Other functions, like alternate lot design and lights on the stations to indicate who needs plug service, can come later.

Non-electric drivers might block the waiting spots, of course, even though they would be marked as for waiting electric cars only. They sometimes even "ICE" block the charging stations. The system can spot that and send enforcement -- even send pictures of licence plates. However, if that happens, the owners can be signalled on their phones to come and resolve the problem.

Instead of waiting spots there could be a waiting "line," if there is a place to put it. In fact, today that's what happens at very busy chargers, people wait in a line for the next one. So pull your car to the back of the line, do your plug duty, and while you are gone, the line will advance and your car will get to the front, and then take a spot and wait for somebody else to plug it in. Since every arrival and departure gets plug duty, that should happen fast. If it doesn't, you'll get notified.

This would allow more efficient use of the chargers, and allow people visiting them to take longer breaks for shopping or dining without having to worry about the charge cycle on their car.

This approach could also be used with regular level 2 chargers, particularly if those can be placed in a way so that they can reach 4 different cars. I outlined a less involved system without self-driving in this article.

This also opens up better shopping options. For example, a popular supercharger is in Folsom, CA, and everybody going to South Lake Tahoe needs to use it. I like to shop at the Costco near it (there is no Costco at the lake) but the Costco is about a kilometer walk away, which is not practical, and you certainly can't rush out from shopping to move your car. This could solve that. (Or I could switch to Sam's Club, I guess.)

Because the cars will handle backing into the charging spots, it makes it easier to design the lot. (Drivers prefer the stations which have the supercharger on an island which allow you to enter the station forwards rather than backwards.)

You could elect to wait in your car and sit in it while it moves itself to the charging station. You could then plug it in yourself for fastest use. Otherwise it waits for somebody to arrive or leave, or for you to get the signal and come to do the plugging.

It is possible that your car might need to plug in but nobody comes or goes for a long time, delaying your start of charging. This should be very rare since we're talking about an overloaded charging lot. Your phone can alert you, giving you the choice of returning to your car to plug it in. You're not much worse off than if you had to sit in line. However, since many people drive to charging stations by entering them as a navigation destination, a company like Tesla could make note of that and predict when people will arrive. It could even insist you use navigation if you want to be in the queue when you arrive. This would allow the system to warn owners if nobody will be around when their car needs plug service.

Even when there is no line

This functionality is still useful at more lightly used stations which don't get full up. Tesla currently charges a fee if you don't quickly move your car if more than half the stations are in use. The ability of the car to remove itself, once unplugged, would eliminate the need for this fee, or for people to worry about getting back in time to move their vehicle.

Simple version

A simpler version of this would work only in lots where there is another parking space opposite the charging space. Many lots work this way. Once your car was unplugged, if the opposite space was empty, it would then slowly move into it. Somebody else could take the charging space. Once that one was full, if you're still there, you would be told to move your car, unless that owner is there and leaving. This would probably give you a 20-30 minute buffer after your car charges before you have to get back. The driving would be very simple, almost like existing summon, except it must make sure no people or cars are in the short path to the space.

It could also go the other way -- wait in the opposite space. Tesla's network will know how long each car has left on its charge, and who has a free opposite space, and tell you which to take.