# What happens if everyone goes when the light changes to green? **URL:** \ **Category:** Factual Questions\ **Created:** [November 17, 2023, 2:29am UTC](https://boards.straightdope.com/t/what-happens-if-everyone-goes-when-the-light-changes-to-green/993274 "2023-11-17T02:29:52Z")\ **Posts on this page:** 5\ **Page:** 4
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [November 23, 2023, 2:51pm UTC](https://boards.straightdope.com/t/what-happens-if-everyone-goes-when-the-light-changes-to-green/993274/61 "2023-11-23T14:51:57Z")
> [@Chronos](#): > > what constitutes a safe distance for a computer-driven car is much shorter than a safe distance for a human-driven car That’s true on paper, because computers can determine distance and speed of the car in front much faster than human processing time, and can also react to changes much faster than a human. But in practice I’m not sure it’s implemented on the boundary. We just bought a car that automatically brakes if it thinks you are getting too close to the car in front. It consistently leaves a much bigger margin than I do when I drive. I’m not talking about blatantly unsafe practices like tailgating–it brakes sooner than I would in situations like normal stopping when I am queueing at a red light or the car in front is braking. In many decades of driving I have never rear-ended another car. ---
**Author:** ![Al128](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/al128/32/16541_2.png) [@Al128](https://boards.straightdope.com/u/Al128)\ **Post date:** [November 23, 2023, 3:16pm UTC](https://boards.straightdope.com/t/what-happens-if-everyone-goes-when-the-light-changes-to-green/993274/62 "2023-11-23T15:16:32Z")
> [@Babale](#): > > I think based on what we’re seeing with the fledgeling “air taxi” industry that any realistic flying car is going to be self piloted. I am sure the vast majority (or even all) of the companies currebtly going for it will fail, **but is anyone even _attempting_ a model with a driver**? (bolding mine) I think that is economically not feasible (think of the delta in riding fees w/ vs. w/out pilot!) … if you have to employ a highly paid professional pilot … (as opposed to a “free” AI-pilot) ---
**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\ **Post date:** [November 23, 2023, 4:33pm UTC](https://boards.straightdope.com/t/what-happens-if-everyone-goes-when-the-light-changes-to-green/993274/63 "2023-11-23T16:33:46Z")
I presume in congested areas would have different levels of flight and there would be approved “corridors” for each direction, in lieu of traffic lights; and approved descent vectors that the corridors bypass, to specific landing spots. Perhaps flying cars would be sufficiently expensive that congestion is less of a problem. But a mess of random point to point flights seems frightening. I prefer the Musk vision of a maze of one-way tunnels criss-crossing under the streets, where only self-driving cars are allowed zipping along at highway speeds under AI traffic control; if necessary, ramp up to the surface roads to complete a journey to less busy areas. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [November 23, 2023, 5:07pm UTC](https://boards.straightdope.com/t/what-happens-if-everyone-goes-when-the-light-changes-to-green/993274/64 "2023-11-23T17:07:25Z")
There is supposed to be a macroscopic relation, valid over a certain-sized region, relating the traffic flow to the traffic density. E.g. [![](https://upload.wikimedia.org/wikipedia/commons/a/a2/Sample_Traffic_Flow_Macroscopic_Fundamental_Diagram.png) ](https://upload.wikimedia.org/wikipedia/commons/a/a2/Sample_Traffic_Flow_Macroscopic_Fundamental_Diagram.png) though the actual shape of the curve will depend on various things. Theoretically, will more computer-controlled cars indeed skew the curve to the right? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 24, 2023, 2:23pm UTC](https://boards.straightdope.com/t/what-happens-if-everyone-goes-when-the-light-changes-to-green/993274/65 "2023-11-24T14:23:50Z")
Could you explain that graph, please? All I can tell from it is that there’s something we’re trying to optimize, and that it has a maximum somewhere in parameter space. [Previous page](https://boards.straightdope.com/t/what-happens-if-everyone-goes-when-the-light-changes-to-green/993274.md?page=3)