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Old January 4th, 2009, 08:25 PM   #241
Natomasken
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Quote:
Originally Posted by ChrisZwolle View Post
The question you have to ask is; "is bus priority important enough to create congestion and extra delays for other road users?". So, would you disrupt a traffic flow on purpose for the sake of bus passengers? It might be justified if there is a busy bus route with lots of passengers, but it might not be justified if that bus usually carries only a few people. However, most policy-makers choose automatically for bus priority, which is in my opinion not always a smart decision.
Policies that attempt to discourage driving are often put in place without a careful, scientific analysis of their impacts. There is an assumption that any policy that discourages driving must be good for the environment. This isn't necessarily the case.

Of course, CO2 emissions are a major concern now, and CO2 emissions are directly related to fuel consumption, which is directly related to vehicle speeds. Look at this chart from the US Dept. of Energy.

image hosted on flickr


This shows that fuel consumption is at its lowest, and fairly constant, between about 30 to 60 mph/50 to 100 kph. Below 30 mph, fuel consumption increases drastically the slower you go, to about 3 times the consumption at 5 mph. So that question that should be asked, but never is, is whether any decreases in fuel consumption that result from the policies (they assume that favoring transit, walking, biking, etc. results is more use of these modes and less driving) are offset by the increases in fuel consumption, and therefore CO2 emissions, due to increased congestion for the majority of people who continue to drive.

In my Sacramento metro area, the governments are strongly anti-car, pro-transit. Although transit accounts for only about 1% of the travel (measured in person-miles) that cars do, they spend far more on transit than roads, under the assumption that this will benefit the environment. But at the same time, the traffic lights in my area of the city function appallingly poorly. Even though they are all controlled by pavement sensors, for some reason they continually stop through traffic on major streets to give a green light to cross streets or left turn lanes where there are no cars. The city could do far more, quicker and more cheaply, to reduce CO2 emissions by fixing these malfunctioning signals, and preventing unnecessary slowing and stopping of vehicles, than they ever will by convincing people to take transit instead of driving. But there is no political will to invest anything in the roads.

I'm not saying these policies should never be used, just that there needs to be an careful analysis of what they are actually achieving, and whether other alternatives, even those that benefit drivers, might be more cost-effective in achieving environmental and mobility benefits. There is an assumption among many of the policy-makers that traffic congestion is actually a good thing because it discourages driving. They have to also recognize that it's also a bad thing, because it increases emissions (air pollutants as well as CO2).

Last edited by Natomasken; January 4th, 2009 at 10:00 PM.
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Old January 4th, 2009, 09:53 PM   #242
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That's exactly what drivers do: pull up inside the intersection and wait for a safe gap to cross; or wait until the opposite traffic stops, and cross during the yellow and red clearance intervals. Here is an example from Japan, which I like that there is pavement marking to indicate where driver should stop inside the intersection but not crossing opposite through travel lane. I wish the US does this in the intersection.
But in Japan the traffic lights are located after the intersection, so it's not a problem to see when they turn to yellow and then red. This is also how it works in Canada. I was referring to countries where the traffic lights are placed before the intersection, in which case you do not know when the lights turn to yellow. In this case you must wait until traffic comes to a complete stop.

And yes, these pavement markings are pretty cool Although they are most effective at huge intersections like the one in the video.
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Old January 4th, 2009, 10:17 PM   #243
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But in Japan the traffic lights are located after the intersection, so it's not a problem to see when they turn to yellow and then red. This is also how it works in Canada. I was referring to countries where the traffic lights are placed before the intersection, in which case you do not know when the lights turn to yellow. In this case you must wait until traffic comes to a complete stop.
Just sit and wait.

There are a lot of old signals still locate in the middle of the intersection not on the far side, which drivers can't see once they are inside the intersection in the tri-state area.
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Old January 4th, 2009, 10:39 PM   #244
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Quote:
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But in Japan the traffic lights are located after the intersection, so it's not a problem to see when they turn to yellow and then red. This is also how it works in Canada. I was referring to countries where the traffic lights are placed before the intersection, in which case you do not know when the lights turn to yellow. In this case you must wait until traffic comes to a complete stop.
With traffic lights before the intersections isn't anything wrong over here; drivers see when the opposite driver is braking for a yellow or red light (nose of vehicle closer to ground than normal, their speed slowing), and very rarely the opposite driver announces he is going to stop by flashing his head lights once or twice. I do this everytime I have to stop (when I know the opposite driver sees me), and it helped quite some times.

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And yes, these pavement markings are pretty cool Although they are most effective at huge intersections like the one in the video.
Agreed.
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Old January 5th, 2009, 07:53 AM   #245
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I filmed this 'walking man' in Abi Dhabi, UAE:

http://vae.autosnelwegen.net/Overig/092.AVI
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Old January 5th, 2009, 01:43 PM   #246
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I still wonder though, how this is done in countries where this "evacuation arrow" does not exist. I presume that one just waits for all traffic to stop and then completes the turn, though knowing when the light actually changes is useful I think. In Canada we don't have this problem because the lights are always placed after the intersection, so you just complete the turn when the light changes to amber/red and all oncoming traffic stops.
A slight variation of this and the traditional practice of going whenever the oncoming traffic can be observed at hook turn (right turn from left lane, left turn from right lane in countries that drive on the right) intersections in Melbourne. You don't get to complete your turn until the lights turn green on the road you're turning into.

My guess is that this is to protect drivers from other vehicles which rush through the amber light because a collision would mean an impact on the driver's side door.
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Old January 5th, 2009, 04:03 PM   #247
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I filmed this 'walking man' in Abi Dhabi, UAE:

http://vae.autosnelwegen.net/Overig/092.AVI
Those looked kinda cool.
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Old January 5th, 2009, 08:08 PM   #248
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Of course, CO2 emissions are a major concern now, and CO2 emissions are directly related to fuel consumption, which is directly related to vehicle speeds. Look at this chart from the US Dept. of Energy.

image hosted on flickr

Besides the CO2 emissions and fuel consumptions related to any given speed, the rate also increases by accelerating. A lot of stop-and-go traffic, typical near traffic lights, also increases the local CO2 emissions.

My city's government compiled a list of the places where PM10 and NOx are exceeded. They are not along the motorway with 110,000 vehicles a day, but on the ringroad with typically 30,000 - 40,000 vehicles a day at the traffic lights. But the worst place was, believe it or not, the access route to the trainstation that carries most of the buses travelling through our city.
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Old January 6th, 2009, 08:24 AM   #249
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Besides the CO2 emissions and fuel consumptions related to any given speed, the rate also increases by accelerating. A lot of stop-and-go traffic, typical near traffic lights, also increases the local CO2 emissions.

My city's government compiled a list of the places where PM10 and NOx are exceeded. They are not along the motorway with 110,000 vehicles a day, but on the ringroad with typically 30,000 - 40,000 vehicles a day at the traffic lights. But the worst place was, believe it or not, the access route to the trainstation that carries most of the buses travelling through our city.
I'm not surprised. It was hard to find research on this, but I found a study once that showed a car being stopped at an intersection generated several times the pollution of a car going through without having to stop. This is one big reason I think environmentalists ought to be among the biggest supporters of motorway building! Fewer emissions per vehicle mile than traveling on surface roads. In addition, because the capacity per lane mile is so much greater than a road with signalized intersections, it takes less road space to move the same number of vehicles (although, granted, the lane widths and rights-of-way have to be a bit larger). Plus, they are safer and and improve urban environments by removing traffic from local streets.

Another factor is that buses are not necessarily less polluting than cars when measured on a per person-mile-of-travel basis. The chart below shows that, in the US anyway, when measured on this basis, motor buses generate more CO2 than passenger cars! Of course the data would be different for Europe, because buses probably carry heavier average loads than in the US (average bus capacity here is over 40 but average load is only 8-9 passengers). But on the other hand, the average European passenger car no doubt generates less C02 than the average US car. In any event, automobile C02 emissions will drop in the future in both Europe and US (due to recently tightened fuel economy standards). It's not clear this will also happen for transit buses. Also note in the chart how a Prius (lowest CO2 emission vehicle in US) puts out barely more than half the CO2 of the average car.

image hosted on flickr


(In the chart, light trucks=pickups and SUV's, and automobiles=light trucks and passenger cars. Also, trolley bus=electrically powered and motor bus=diesel powered (?))
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Old January 6th, 2009, 09:11 AM   #250
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It also depends what fuel buses are driving on. Diesel isn't the best, but we have hydrogenpowered buses too, which reduced the PM10/NOx pollution in the city of Haarlem by - I believe - 50%!

Also, it matters if trains are powered by coal plants, hydroelectricity or nuclear power. In Switzerland, the train fleet is nearly CO2 free due to hydroelectricity, but in the Netherlands, most energy comes from coal and gas power stations, hence the train network is by far not CO2 free.
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Old January 6th, 2009, 10:06 AM   #251
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It also depends what fuel buses are driving on. Diesel isn't the best, but we have hydrogenpowered buses too, which reduced the PM10/NOx pollution in the city of Haarlem by - I believe - 50%!

Also, it matters if trains are powered by coal plants, hydroelectricity or nuclear power. In Switzerland, the train fleet is nearly CO2 free due to hydroelectricity, but in the Netherlands, most energy comes from coal and gas power stations, hence the train network is by far not CO2 free.
Right, those figures in the table are national averages, but vary widely from place to place. Eastern US uses a lot of coal power generation, but Western US has a lot of hydro power, especially in the Pacific Northwest. Likewise, because of our bad air quality, all of the buses (I think) in Sacramento run on compressed natural gas. This is probably also true in other places in California. I think there are also hybrid-diesel buses used in some places.

Here's a link to access the whole report I took the table from, if anyone's interested.

http://www.cato.org/pub_display.php?pub_id=9325
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Old January 18th, 2009, 11:57 PM   #252
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Ive not posted for such a long time

Anyway, nice Hong Kong pics a few pages back!

All based on UK specs though, from when it was a crown dependancy of the UK.

And bus priority doesnt nessicerily mean the bus has to be tagged. It will work of a system by PEEK called PRISM, in which detectors pick up the shassie of the vehicle and cross-reference it with the UTC SCOOT or UTCC database of authorised vehicles, and thus allow priority.
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Old January 19th, 2009, 12:08 AM   #253
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Just a few points to ponder

Traffic lights in Doha, Qatar are painfully long and i wouldnt be surprised if they take the longest amount of time to change anywhere in the world.

Also traffic light in South Africa are called "Robots".
Dont think they are called that anywhere else
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Old January 19th, 2009, 12:33 AM   #254
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Yeah.

Robots. Some people from the USA mistook the Robot thing to be British termanology. It is not though. They are called Traffic Lights here, by nearly everyone. However technical people will call them Signals, Lanterns being heads, and Lamps being bulbs.
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Old January 19th, 2009, 01:25 AM   #255
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There's an official traffic light man here now? LOL!
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Old January 19th, 2009, 08:46 AM   #256
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A famous traffic light in Nagoya:


Quote:
Originally Posted by tjkb230 View Post
Take a look at this
Japanese traffic light!
But who can explain why the traffic lights behave like this?
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I think the arrows go on first to indicate a protected phase: the drivers to whom the lights are dedicated to can turn safely in the direction of the arrows. It's actually visible by looking at the cars coming from the other side. They remain stationair until the main green signal is active. And I think the amber and red phase between the green arrows and the main green signal is to indicate that the protected phase is about to end, because the drivers (nearly) keep on driving through this phase.
Yes, that's exactly how it works.
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Old January 20th, 2009, 01:32 AM   #257
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There's an official traffic light man here now? LOL!
Yes

I have, incidently, and unless anyone else knows otherwise, the largest collection of signals in the UK... 34 at the moment, 3 matrix signs, 4 street lights and 59 road work lamps... Scary I know


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A famous traffic light in Nagoya:
I have to say, that is a very good signal. However, if the Ped phase is concurrent with the Vehicular phase in one stage, then why can't pedestrians just use the Vehicular signals to tell them when to and when not to cross? I assume these have a flashing green/red man before going to red however, and I can see the advantages.
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Old January 22nd, 2009, 05:58 PM   #258
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Here's a question: how long does the amber phase last where you live?

In Queensland, Australia, the amber phase is 4 seconds on roads with a speed limit of 60km/h or less, and 5 seconds of roads with a speed limit of 70km/h or more.
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Old January 22nd, 2009, 06:01 PM   #259
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Netherlands:

50 km/h
through: 4 seconds
turning: 3 seconds

70 km/h
through: 5 seconds
turning: 4 seconds
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Old January 23rd, 2009, 06:31 PM   #260
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Quote:
Originally Posted by ChrisZwolle View Post
Netherlands:

50 km/h
through: 4 seconds
turning: 3 seconds

70 km/h
through: 5 seconds
turning: 4 seconds
In Belgium, this is either 3 or 4 or (very sometimes) even 5 seconds, depending on the length of the green.
2 minutes or less: (non-)busy road = 3 seconds.
2 to 3 minutes: non-busy road = 3 seconds, busy road = 4 seconds.
Longer than 3 minutes: (non-)busy road = 4 seconds.

Many times, when speeds up to 120 km/h are allowed on the road, they're lowered to 90 km/h, and there's also 2 warning lights accompanied with the "Traffic Signals Ahead"-sign, and they're both placed to the right of and above the road, to warn the drivers there's either road-works, danger or a traffic signal-controlled junction ahead.
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