War on Short yellow lights.

Well then, your traffic engineers are dumber than ours. But that was my point anyway. There are NO standards (safety or otherwise) that these people seem to follow. Its one thing if they are haywiring signals paid for with local funds. But when the feds kick in a big chunk of funds, I think we need to make sure we're getting our money's worth.

I witnessed such a "turner" into a crosswalk with "Walk" on, AND manned by a crossing guard (school zone), hit a kid pushing his bicycle :-(

"Turner" didn't stop for awhile... finally did because crossing guard chased him down the street whacking the side of the car with his big Stop" sign ;-)

I had also assumed chase mode (in my 280Z). When the guard got the perp to stop, I blocked his path.

When the cops arrived, they jumped out and asked, "Jim, What happened?"

(I regularly drove 18th St, Highland, 24th St, and Lincoln from 1977 to 1984, stopped at every accident I saw (nasty area for idiots), and became known by the cops as a reliable witness ;-)

Fortunately the kid was not seriously hurt.

...Jim Thompson

You shouldn't get to the point where you lose traction; if you ease off the brake enough to regain traction, you'll decelerate faster.

The point is that, so long as the brakes are capable of gripping the disc/drum hard enough that you *could* lock the wheel, the brakes aren't the limiting factor. Stronger brakes won't make you stop any quicker.

Essentially, the best brakes and the best tyres will only provide a small improvement over adequate brakes and adequate tyres.

If you're driving something with distinctly below-average braking ability, you would normally slow down more than an average car would in any situation where you might expect to brake, which would include approaching traffic lights.

A speed limit is a *limit*, not a target. There are other factors which affect what is a sensible speed, including the probability that you will need to brake.

No. They should be set such that most vehicles could stop in time without having to brake exceptionally hard provided they are driving either within the speed limit or at the prevailing traffic speed (vehicles driving a bit faster will have to brake a bit harder). If you're driving a vehicle which is significantly atypical, you need to allow for that in the way that you drive.

This isn't just an issue of the vehicle's physics. E.g. if you're transporting animals, you wouldn't subject them to the same level of braking or cornering forces which might be acceptable for a seated (and restrained) passenger.

Only if they're driving too fast. A speed limit of e.g. 55mph means that it's likely to be safe for many vehicles to drive at that speed in good conditions (traffic, weather, light), not that it's safe for all vehicles to drive at that speed in all conditions. For some vehicles, that speed may not be safe in any conditions.

Well, define "regular". Some people maintain and use vehicles from an era where road traffic was mainly horse-drawn. The Model T was originally designed for that era, and was largely responsible for the end of that era.

If you're trying to prevent people from running stop lights (rather than encouraging it to increase revenue from fines), the most important factor is consistency. If yellow lights always lasted 2 seconds, drivers would automatically slow down every time they approached a set of lights, in the same way that you automatically slow down when approaching a blind bend.

Beyond that, the timing should be long enough that the vast majority of vehicles can maintain their speed upon approach when the light is green. IOW, the proportion of vehicles which need to reduce speed "just in case" should be low enough not to substantially reduce traffic flow.

This is really an efficiency issue, not a safety one. The only safety issues are:

1. Yellow lights which are significantly shorter than drivers expect, leading them to maintain speed on the (incorrect) assumption that they will cross the junction before the light turns red. When the assumption turns out to be incorrect, it may be too late to stop in time.
2. Drivers who drive too fast for the road conditions. That may include people who think that you can drive a vintage car like a modern car, but personally I doubt it. Most people are capable of gauging their braking ability and reducing speed accordingly, and the ones who aren't are unsafe in any vehicle.

is

Somehow, I think their braking *is* worse, but I'm no expert. When a tire is locked up and skidding, I think the area of the contact patch, and the nature of the tire's rubber compound, has an effect on stopping ability. Model T's have narrow tires, and I suspect this has an effect.

I'm not sure what you mean by this. We're talking about the ability to stop at a light. The way you drive a modern car is to drive at the speed limit as you approach the intersection. Wouldn't you drive a Model T the same way? I'm not concerned with how closely one ought to follow other cars vis a vis the car's braking capability. I'm only talking about the ability of a lone car, with no other cars around, to stop during the duration of the yellow light, when the car was going the speed limit just before the light turned.

This is a news group frequented by engineers, who generally are familiar with the concept of worst case design. What I'm asking is, shouldn't the traffic light timing be such that a car with the worst braking capability which is legally allowed, driven by the person with the longest reaction time who is legally allowed to drive, be able to stop during the yellow?

If the timing is set so that a car+driver with average capability is just able to get stopped, then those with less capability (but who still meet the minimum legal requirements) will be guaranteed to not be able to stop in time.

As I say above, even though concerns such as how closely to follow are relevant in the total driving experience, all I am talking about here is stopping at red lights, and I'm only concerned with regular 4 wheel passenger cars.

Only if the vehicle (and I'm only talking about passenger cars, not construction or farm vehicles, etc.) fails to meet the minimum legal requirements to be on the road. If it's so atypical that the driver needs to slow down as he approaches every traffic light, he is in danger of getting a ticket for impeding traffic. That vehicle probably isn't legal to drive on that road.

My point is that I believe the lights should be set so that *all* passenger cars which are legal should be able to stop in time, not just *most* of them.

If you disagree, then we disagree.

You're expanding the scope of the discussion beyond the point I'm trying to make. You're certainly entitled to do that, but it isn't relevant to the my point, and it just clutters the discussion. I'm trying to keep to one simple point. Vehicles transporting animals are another issue, and I wouldn't expect traffic lights to be set to accommodate them. Drivers of such vehicles will indeed be expected to drive in a different manner than a passenger car will be driven. It's only passenger cars that I am considering.

Then those vehicles wouldn't be legal to drive on that road. I specifically said that I was considering vehicles that meet the minimum legal requirements Driving substantially below the speed limit gets you a ticket for impeding traffic. And, I mean passenger cars, not construction vehicles that just can't go the speed limit, and drive below the speed limit with flashing lights, or other similar vehicles.

At the particular light that frosts me, I have observed semi's sliding, because the drivers (regular Safeway trucks, for instance) know it's a rigged light.

I await a major accident with deaths, then I'm going to dump all over the City of Phoenix... because they've flipped me off every time I've raised the issue.

...Jim Thompson

will=20

your=20

have

that

Thanks to some knowledge and a quick search, try:=20

Document it (and the fact that the city *knows* and doesn't care) in the usual legal ways and you'll make some lawyer very happy, even if the widow isn't. The residents of Phoenix may not deserve the inevitable few $M payout but maybe they'll learn a lesson and dump the politicians.

Make sure you've raised the issue in a letter sent by registered post.

Notify your local newspaper.

Sylvia.

I don't know about the US, but the UK seldom (if ever) makes roadworthiness standards retroactive. If a vehicle complied with the standards in force (if there were any) at the time it was first used, it would still be legal to use it.

All vehicles can stop in time, provided that they aren't driving too fast. Some vehicles may not be able to stop in time if they're driving close to the speed limit; that just means that they shouldn't be driving that fast.

But then you bring up vintage vehicles, which are even more atypical.

Speed limits and traffic light timings are based upon typical vehicles, typical drivers, typical conditions. If you assume the worst case, traffic lights would only have two phases: yellow and red.

Not necessarily. There are likely to be a whole host of exemptions and special cases. Also, road conditions are a factor, and traffic light timings don't normally adjust for them.

FWIW, there is a table of minimum timings on page 90 ("Page 4D-50"):

speed time 25 3.0 30 3.2 35 3.6 40 3.9 45 4.3 50 4.7 55 5.0 60 5.4 65 5.8

It gives the basis for these timings as 1 second reaction time and

krw wrote in news: snipped-for-privacy@4ax.com:

If it's a rigged light(short yellow),film it for documentation,then sue the city/county.A good lawyer could surely find an applicable law they are violating.

...Jim Thompson

Good idea. I have already timed it for several hours to make sure it wasn't variable.

...Jim Thompson

I didn't say anything about retroactivity of standards, but as far as I know, here in the U.S., cars have to meet standards in force now. If they don't, they may still be able to be driven by having yellow flashing warning lights and a sign warning of a slow vehicle. But, that's not what I'm talking about.

The California Highway Patrol was known for giving Yugos tickets on the freeway because they couldn't maintain the speed limit on hills. Model Ts might not be able to maintain on those hills either. Just because the Model T met the standards in effect when they were being manufactured doesn't mean that they are legal on every road today.

A car may be illegal to drive on a particular road (without the flashing lights, etc.), not necessarily just because it's vintage, but because as a vintage car, it doesn't have the capability for modern roads. A more modern car may also be illegal on some roads because it's crappy and lacks some required capability. There are signs in some states at on ramps to highways warning that vehicles (typically motorcycles) with horsepower below some limit are illegal on that highway.

Of course; this is a tautology, and not relevant to the discussion.

If they are a passenger car, not driven near the speed limit, and not running with warning lights, they are in danger of receiving a ticket for impeding traffic. I repeat: I'm only talking about passenger cars, which can drive at the speed limit, and which meet the minimum legal requirements for driver reaction time and braking capability to be on the road, but which are not as good as the average in those respects (even though they still meet the *minimum* legal requirements). Such a vehicle *should* drive at the speed limit to avoid a ticket for impeding traffic, and the timing of the yellow traffic light should accommodate them even if they are somewhat slower to stop than average.

Again, I believe the timing of the yellow light should be such that on dry roads, with pavement in good condition, a passenger car+driver that just meets the minimum requirements to legally drive on a given road, travelling at the speed limit when approaching the light, should be able to stop safely without running the red light.

I suspect that the factor most likely to lead to inability to stop in time is driver reaction time. The legal requirements allow for reaction time, and there is a maximum reaction time which is still legal. Anyone who is slower than that shouldn't be on the road, but if they meet the requirement, then the timing of the yellow should be long enough to allow them to stop without running the red.

I have no objection to bringing up atypical vehicles, as long as they are passenger cars which meet the minimum legal standards. The passenger cars at the bottom end of the scale of legal requirements are atypical. That's why I'm talking about them.

As I mention above, flashing lights and "slow vehicle" signs allow for operation of otherwise illegal vehicles on the road. I'm not concerned with those cases.

As to road conditions, I'm only considering dry pavement on non-rainy days, so it's irrelevant to my discussion whether traffic lights might or might not adjust to other conditions (although it might be a good idea).

In a lot of cases, there's a significant difference between what _should_ be and what actually _is_.

Cheers! Rich

Now that Homeland Security has right-wing extremists on their terrorism threat list, maybe they'll get JT out of our hair. >:->

Cheers! Rich

No lawyer is going to get a woody until someone dies. Then they'll be coming out of the woodwork.

they

are

lights,

The UK has something similar, but weaker. Motorways can only be used by vehicles capable of at least 30mph, and not by mopeds (which are limited to 30mph by law), cycles, or horse-drawn vehicles. Some other roads may have minimum speed limits and specific prohibitions, but these are quite rare.

But motorways don't have traffic lights, roundabouts, junctions, etc, just slip-roads (on/off-ramps).

Actually, it's quite fundamental to the discussion. The arithmetic of whether you or not you can avoid running a red light depends entirely upon speed.

should

If that's the case, the situation in the US would appear to be somewhat stricter than the UK (or AFAIK most of Europe), where you would only be committing an offence if you were driving slowly without reason, or were below a statutory minimum speed limit (which are never above 30mph, and those are on roads with a 70mph limit).

Roads other than motorways have to accomodate all kinds of traffic, as there may simply be no other route to get from A to B. Yellow warning lights are normally only seen on wide loads, or vehicles driving unusually slowly on motorways by permit (if the load is large, alternative routes may be impractical).

If you're going to require all vehicles to drive close to the speed limit, then realistically you also need to require vehicles to have braking to match.

Traffic lights aren't the only reason that a vehicle may need to stop. If it's braking means that it can't stop for a red light at the prevailing traffic speed, it's also going to have trouble stopping at that speed for any other reason. If there are any junctions which aren't controlled by traffic lights, vehicles entering or crossing such junctions aren't going to know about the braking ability of an approaching vehicle.

there

that

I suspect that the main factor is variation in timings: drivers not knowing that the yellow period is short, maintaining speed on the assumption that they can clear the junction before the light turns red, then having it turn red just as they're about to cross the junction at speed.

The UK doesn't have the problem with each town setting its own timings (sometimes rigged to increase revenue from fines); traffic laws and standards are determined nationally.

If the yellow light is timing is remotely sane, then crossing the line as you skid to a halt should be unlikely in any vehicle. Any driver should have a reasonable idea of their stopping distance given the speed, vehicle and road conditions. If, at the point that the light turns yellow, you're close enough to the junction that you might have to brake hard, then a sane timing would allow you to maintain speed and clear the junction well before the light turns red.

The 10ft/s/s deceleration given by the California code posted elsewhere in this thread is less than half that used for calculating standard stopping distances. If a vehicle can't even manage that, it's *very* atypical. We're talking about vehicles whose maximum deceleration is less than the way that people brake for traffic lights, which is usually a lot less than their maximum braking.

It's probably impractical. E.g. after snowfall, road conditions can vary between normal and sheet ice within the space of 100m. In rain, the amount of surface water can vary similarly.