

Automated cars would call ahead and schedule a time for the intersection


Source: University of Texas at Austin

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RE: Pedestrian interface
By kattanna on 2/21/2012 11:18:55 AM , Rating: 2
One purpose of stoplights is to tell the pedestrians when they can cross

true. but the main purpose is to tell opposing traffic when to stop.

with our perpendicular street intersections you will always need some mechanism to tell when one path can go and the other to stop, even those small 1 stop sign towns LOL

thats why the freeways are not built that way, but instead with off/on ramps that allow the smoother free flow of traffic.

this system might work in those small 1 stop sign towns as there is little traffic, but in places like Los Angeles or, LOL, NY. please the shear demand is huge

RE: Pedestrian interface
By twhittet on 2/21/2012 1:02:14 PM , Rating: 2
In a fully automated system, it will be designed to handle this. When conditions are ideal (no snow or ice), cars will be synchronized and be able to easily take turns going through intersections without ever stopping.

Pedestrian traffic and other obstacles ("legacy" vehicles without smart control, slow moving vehicles, etc.) will be the most difficult to engineer around, but not impossible.

RE: Pedestrian interface
By drycrust3 on 2/21/2012 2:34:20 PM , Rating: 3

Believe it or not, this is already partially implemented for buses. At least it is for the buses I drive in New Zealand, and I don't think we are the only place in the world that does this.
The bus has a GPS system and that is linked into the traffic light system. As my bus approaches an intersection the traffic lights actually make allowance for the bus, and as long as the bus isn't too far away, then if the lights are green they will hold green just a bit longer than they'd otherwise do, and if the lights are red and the bus is waiting, then they will cycle around quicker than they'd otherwise do.
One way easy way to tell when the system is working is to watch the lights as the bus approaches the intersection, and if they turn yellow about when the bus is just 1 to 2 metres before entering the intersection then that is a pretty good clue that there is some sort of computer - bus communication. Of course, a good bus driver could just have seen the lights were about to change and sped up a tiny fraction to get into the intersection as the lights were going yellow.
There are several problems with this technology. The first is the assumption that every vehicle is travelling at about the speed limit e.g. 50 km/hr, and that they will have cleared the intersection when the lights go red. Reality is vehicles may not be travelling at this speed, they could easily be travelling slower. For example, the vehicle may want to turn at the intersection; or a bus could have stopped to let passengers off at a bus stop and the distance between the bus stop and the lights is such the bus can't get up to the expected speed, so the lights start changing too early; or there is a queue of traffic on the other side of the intersection which means a vehicle can't exit the intersection at 50 km/hr; or the terrain and the power to weight ratio of the vehicle is such that 50 km/hr is impossible e.g. a person riding a push bike up a hill.
Another problem is the traffic light system can get overloaded in peak hours, meaning the priority phasing for the buses doesn't always work.
A third problem is what I call "the second bus" problem, which happens when two or more buses are approaching an intersection, and the lights will only wait for the first one and not the second one.
There was another problem that occurred with the previous "silver box" system we had (the bus had a "silver box" under the front of the bus, and that controlled the traffic lights through the induction coils under the road), but I haven't noticed it with the GPS system, which involved one bus overtaking another bus when close to the traffic lights (e.g. two buses in adjacent lanes where the traffic travels at different speeds). Say two buses approach an intersection, with one ahead of the other. The traffic lights pick up the first one and start waiting, then they pick up a second bus (the buses would pass information such as who they were, so the lights could differentiate between the buses), so then the lights forget completely about the first bus and start waiting for the second one instead, but then the second one overtakes the first bus, and so the lights change phase when the second bus hits the white line going into the intersection (or just before it) and thus the bus that was first has to stop.

