To highlight one other point from the video: You want a light to be able to clear the line built up each time. If not, flux in > flux out and that's a recipe for a growing line, which causes a traffic jam.
Ideally, yes, practically, no. In reality you also have to consider what comes downstream of a traffic light. It doesn't help at all if one traffic light has perfect throughput only to put everything into gridlock in the next node.
That means in most real traffic systems each intersection lane will have to have less then ideal throughput because you don't want to overwhelm the next section, as this could be even worse for the system overall.
If you have some engineering background you can also think about this as impedance matching. If you have a 4 lane road narrowing to 2 lanes you have a sudden impedance increase, leading to flow issues. If you put an intersection inbetween you now have a way to manage that impedance mismatch with signaling times, but you have to both look at the impedance before and after the intersection.
Who claimed it was tho? We were talking about throughput. If all your intersection knows is time, it can't decide based on traffic. Which is why inductive loops, camera based systems and so on exist, but (1) they are not deployed everywhere and (2) if they are deployed there may still be a time based limit for the case of defective sensors.
Our traffic systems are already pretty well optimized where we are willing to spend money on them. Note however that if you 100% optimize any system for perfect throughput, it has zero slack to deal with unexpected fluctuations in traffic patterns. That is as true for traffic as it is for networks. Throughput is important, but so is comfort, resilience, predictability and cost. All different metrics you have to keep in mind¹ and all of them can suffer when you over-optimize for one.
The view from inside the traffic that we are part of may make that seem inefficient, but seen system wide the main problems usually are not traffic lights, but harder to change structural issues.
¹: or rather you don't have to keep them in mind, since there are people who specialize on just that and are pretty good at it
The second reason: trying to incentivize people onto trains, buses, bikes, foot, etc.
Cambridge, MA does this. The light are purposefully timed to not let you travel through multiple greens on the tertiary roads in particular, less so secondary, etc.
Cambridge also gives a substantial amount of time to pedestrians as part of every cycle- no "beg button", because the city does not consider someone on foot to be less deserving of crossing time - specifically to not have the car "be king". By making it relatively fast to get around on foot, they reduce the incentive to drive.
They also heavily structure the residential neighborhood streets with one-way directions designed to make it very difficult to use the streets people live on as cut-throughs when the main roads jam up because that leads to noise, pollution, and danger to people on foot and bike, particularly because the kind of person to use a neighborhood as a cut-through is likely also driving quickly and aggressively.
The Old County lights at least are staggered so they are almost always green at the same time. The Central Expressway ones, not so much - there've been times I've been stuck for 20 minutes trying to cross the 100 feet from Moffett to Castro in Mountain View, because the light timing never lined up with the train signals.
They've conveniently solved this by closing the Moffett->Castro side of that intersection entirely. You can still go Castro->Moffett, but they're planning on closing that to eliminate the grade crossing entirely.
Is there still pedestrian access from the northeast side of the Caltrain? I used to live in the Moffett/Middlefield area and being able to walk to downtown was a big draw for that.
Yeah, they're planning to put a ramp from the Shoreline bridge over the tracks down to Evelyn to spread out the traffic, but right now people take Villa.
> Is there still pedestrian access from the northeast side of the Caltrain?
Yeah, all the crosswalks are still operational. The long term plan is to put a bike/ped tunnel under Central and to completely close off the Castro/Caltrain side.