Bicycles in the Robocar world


A recent article on bicycles and pedestrians in the robocar world appears at the Greater Washington web site, which has taken an interest in robocar topics. In particular they are concerned about the vision of a reservation-based intersection, which does not use traffic signals. These designs from U of Texas got a lot of press in the last few weeks after a presentation at AAAS, but they've been around for years and I have a number of links to them. What's new is that the coming of robocars makes them seem more practical.

In a reservation based intersection, the computer handling the intersection hands out slots to cross the intersection. The slots are moving boxes that you have reserved, and you cross in them. The computer hands out the boxes so they never hit one another. The simulated result at first would scare people to death but over time they might trust it. However, it requires that every car on the road have automatic operation, since deviation from your reserved box does indeed mean serious risk. Human judgement just would not cut it here. As such, intersections like this are a long, long way away.

Closer, I think, is the concept of reservation based roads. These are road segments which hand out long term slots, such as "You can drive this block between 8:30 and 9am." The road only hands out as many slots as it can handle, but does not try to schedule the cars down to the square foot-second. In such a system, as you approach that block on your trip, you would refine and correct the initial reservation, so that by the time you are a minute away, your window is just a few minutes. If roads can do this they can assure, well in advance, that they never get more cars on them than they can handle, and this reduces the odds that traffic will collapse due to congestion. The biggest cause of congestion is basic excess of demand over supply -- accidents are the #2 cause.

Such a system can also handle human driven cars. Those cars are a bit less predictable and need wider reservation windows. They also will eventually need more space on the road, since robocars will eventually start packing themselves closer together once they are common enough to do that. Half-width robocars will commonly pair up in a lane with other half-width vehicles.

So what about the bicycles? It will be daunting for them. If there is a bike lane, that's great of course. And at "bike rush hour" we can even make sure "parked" robocars get out of the way to make a bike lane if that's what we want. (We may want another car lane even more.) Otherwise a virtual bike lane can be made if the bikes have to ride with the traffic.

Bikes do present a safety issue to be sure. In the worst case situation, a cyclist can fall off their bike and stop immediately, lying in the road. A vehicle following a bike has to leave enough space to assure they can stop before that, including reaction time. Reaction time should be better for robocars than for humans. Humans don't leave enough space right now. We leave even less space behind cars because cars actually can't stop super fast, and you brake with them. and if you hit them at slow speeds it's "tolerable" -- nobody will be seriously hurt. Hitting a cyclist or pedestrian at slow speeds can mean death.

(Head-on collisions are a different matter and they can cause great mayhem. I believe that moving mostly to one-way streets is the best solution to the problem of head-ons, and with robocars, the inconvenience of one-way streets can be greatly reduced.)

Robocars should end up much better at spotting cyclists than humans are, because robocar vision is 360 degrees and in 3-D. There are no blind spots in a robocar system and it's always paying attention in all directions. The only negative in spotting them is their small size. A bike that appears out of nowhere from behind an obstruction is always at risk to both robocars and human drivers. Robocars will work very hard to not hit cyclists, and in fact in the future street that's 100% robocar, a cyclists should feel pretty safe, and could even abuse the system, weaving back and forth and causing jolts for the passengers around the bike.

On the plus side, robocars might enable two things. The first would be the creation of dedicated lanes, paths and even elevated guideways for use by both bicycles and narrow lightweight robocar trikes. I anticipate these lightweight vehicles will become very common, as they are the most efficient vehicle for short urban trips. Because they are light and small, it's vastly cheaper to build dedicated pathways and elevated guideways for them. These guideways could be made open to bikes if there are passing zones, since the robocars would sustain higher speeds. (We have not yet convinced many US cities to dedicate a lot of space and money to bike-only paths, otherwise that would be obviously better for bikes.) Robocar only lanes offer a cheap way to increase road capacity and offer ultralight robocar users a faster, zero-congestion trip in the busiest areas, and thus make a lot of sense for cities. The bang/buck is as high as it can get in transportation development, and it encourages green transportation, as these trikes use less energy/person than transit systems do.

Another interesting development might be the bike-bot. As I envision it, this is a very small robot that's able to clamp onto a bicycle and move the bike from place to place, using the bicycle's wheels as well as its own. This could offer a world of "bikes on demand." No matter where you are, you could summon up a bicycle in a short time, and drop it anywhere. (At your destination, you would insert the bike into a bike-bot that sent itself there ahead of your arrival, and the bike-bot would take the bike to its next rider.) This could make bicycle use very convenient, and would be good, efficient exercise for all who need it.

I also suspect that we'll see ultralight robocars that feature pedals. With the pedals, the rider would have the option of exercising and their energy would also go into powering the vehicle. The commute is a good time to exercise and watch videos or read. Not as much fun as recreational cycling, but more pleasant in other ways that cycle-commuting.

In the more distant future, when all cars are robocars, we will begin to see the conflict between the cars and the bikes and pedestrians described in the article cited above. The author is right that putting pedestrians on elevated bridges is not a good answer, and forcing bikes off valuable road is not good either. In an idealized robocar road, which has no parked cars on the side, and just many lanes of one-way traffic, the presence of the cyclist does use up a lot more road capacity per person than the cars do. We're a long way from that idealized capacity, but should we come to depend on it, we might see pressure to push the bikes away, or charge them or the amount of square-foot-seconds of road they use. That will be a political decision, where we may decide many decades from now that to encourage cycling, it's worth subsidizing it a bit.


Why would this be necessary when all the cars communicate with one another?

If my car knows about all the other cars then what would be the point of having a central computer that knows about all the cars passing out "reservations" for an intersection.

Like you said, not everything will line up exactly, so the boxes would have to be bigger than optimal.

When each car approaches the intersection, *then* it will do the calculation to adjust speed as necessary based on all the other cars nearby.

I agree that this will be quite scary at first, especially if the cars can zipper through an intersection at 50 MPH missing each other by a few feet. I can't wait.


I would model the air traffic control system, where a tower controls all the airplanes in a given area. Imagine the robocar on approach to an intersection. It communicates with a local control node (for that intersection, or a smallish group of intersections) to plot a route through the area. The control node gives the car computer a more precise route and speed to avoid collisions with other robocars moving through the intersection. The robocar and control node have to be in constant communication. This will permit the system to adjust rapidly should there be a collision, or other unforeseen roadway obstruction, such as a bicycle or pedestrian.

I think the pedestrian problem is simple to solve. Walk/Don't walk signs can be used to tell them when it is safe to move. The robocar traffic will just have to stop. Bridges and raised walkways are fine for very busy intersections, but not practical for all areas. Bicycles are tricky though. Perhaps the bicycle can have a transponder that can tell the system when it is near and its desired path. A stop light mounted on the bicycle can tell the rider when it is safe to move through the intersection. There could be lights embedded in the roadway for the cyclist to follow, that create a dynamic safe path through the traffic. Again, traffic may just have to stop and wait for the bikes to move through.

Runners, pedestrians, jaywalkers, deer, skunks, tires, pallets, mufflers, rocks, fallen trees, falling trees, branches, open manholes, construction cones, cows, tractors, buggies, oversize loads, spills, potholes, motorcyclists, skateboarders, trains, snow, ice, floods, erosion, etc., ...and bicyclists. There's a lot of potential trouble out there that must be sensed and interpreted before robocars can share unlimited-access roads, with their "own lanes" (as if) or not.

I still don't understand the purpose of the control tower just for intersections. It seems redundant.

Recently, I read an article (maybe here) that described how all the cars would communicate with each other via low powered radio, so they would all already know about each others speed, location, path *and* pedestrians and bicycles. When something unexpected occurs, all the cars who witnessed it would communicate that to the other cars so they can react appropriately. No control tower necessary.

I imagine that there will be a central control that will coordinate the major roads in a community especially when there is an accident or bad weather, but it should *not* try to control the local traffic. A distributed system would be better and more reliable.

At the intersections, the pedestrians can punch the button to activate the Walk light just like everyone does now.

The bicycles are a special case. I can't see a biker simply closing his eyes and crossing, hoping that all the cars see him and slow or stop as necessary. I'm sure that they don't want to be relegated to hitting a button like the pedestrians. I can see them having a low power transmitter that activates the walk light.

I love this discussion!


I would be interested in seeing proposals for a fully distributed system. Keep in mind that car to car communication is slightly less reliable than car to infrastructure, but let's assume we can solve that.

The usual reason for the central system is that like the traffic light, you want to hand out reservations in a fair way, and a way which balances the flow in other intersections, too. Any given car would love to just barrel through the intersection, and tell all other cars "I am going through at 60mph starting at time t." But what if another car is coming that also would like to cross in a path that will intersect.

The reservation system commands cars to slow down (or sometimes speed up) to make their reservation. It can do so fairly, not favouring any given vehicle or any given direction. It would do it to optimize throughput in the intersection, while individual cars want to optimize their own trip. If you can work out an algorithm that would optimize the intersection while all the cars try to optimize their trip, that would be good.

You might suggest a law require the cars not be selfish. That's a tall order, and hard to enforce if there isn't a system to notice it.

I was thinking that the algorithm for optimizing the traffic flow for major roads would be at least partly specified by the NHTSA. This could be tested monitored by them just like they do other safety features of a car.

The algorithm could allow for certain roads to get higher priority at different times of the day or if there was an accident on a different road that temporarily increased the volume.


There are cars that have pedestrian airbags in development. The airbags deploy when the car senses it hits a bike or pedestrian, so even if the cars don't recognize an object as another car it can communicate with, they can still be made safe. Or at least, the technology is moving in that direction.

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