The shipping company UPS uses software to route its famous brown trucks to minimize time at stoplights. Too bad there isn't an automotive technology that can allow you to turn the engine off when you're stopped. If only...

http://multichannelmerchant.co...serve/

Or the US could start using more roundabouts and then traffic wouldn't need to stop as much no matter where it was turning

Now, if they could only figure out a way to obey traffic/parking laws and not block traffic with an illegally parked truck?
Wonder how many millions of gallons are wasted by the rest of us trying to find a away around their convenient, rolling roadblock?

Efficient drivers do it better.
1003 miles a tank personal record. 74MPG calculated. HCH1 CVT

In most places in my area in southern California, roundabouts would severely inhibit the flow of traffic as they would become gridlocked (much worse than waiting a couple signals), although they do work amazingly well when traffic is fairly light to moderate. Suburban surface streets here routinely have 50mph speed limits, and traffic lights that are synchronized to allow through traffic to go through many consecutive green lights. Also, they have traffic sensors to only allow left-turning when it is actually needed. These intersections run at nearly full capacity all the time, meaning in the morning they will be mostly green in one direction, or will allow protected turns in mostly one direction, depending on where most of the traffic is going, then later in the day, they adapt their schedule to allow traffic to flow in the opposite direction without stopping (for the most part), roundabouts can't make accomodations based on differing direction of flow of traffic at a time, and would become congested with a lower volume of traffic. Also, the roundabouts required to accomodate three lanes of through traffic (not counting turning lanes) at 45-65 miles per hour without slowdown would cover an obscene amount of space, especially if they were required at every major intersection.

As for reducing fuel use by avoiding left turns, the best way to do that is to simply stay in the leftmost lane on the road, and watch for left-turn arrows that are green. Instead of waiting and always turning at a particular intersection, you could turn left earlier, at the first arrow you find that is green, so you don't need to stop, then turn right after that (preferably with a protected turn, again). In my city commutes, there are often several routes that are the same distance -- which direction I choose depends on what the signals are at the time.

Oh no, not more of those dreaded roundabouts (or rotary's as we call them here in Noroadsignachusetts). Total gridlock here with those. I also oppose traffic lights in general. Traffic lights should be set to flash in the evening hours when there is no traffic and also on weekends when traffic tends to be lighter. There must be a laid off NASA rocket scientist out there that can program a traffic light???

Set to flash at night? That would force people to brake to a stop at every single intersection when there is no traffic! Although, for simple lights with no sensors that may be an improvement. Nearly all in Southern California have sensor controls though -- so on major streets late at night, I can often go through 10+ consecutive signals (several miles) before stopping, and when I do have to wait, it's usually only for about 20 seconds for a few cars. They keep the lights green all of the time, unless someone is actually at the cross-street waiting, in which case it will wait until through-traffic passes, then switch for just a few seconds to let the person turn, and switch back.

The only gripe I have about the lights is that the sensors that control them are too close in some cases, so occasionally it will think a road is empty and change the signal as cars are approaching or, if cars are approaching it and it's already red, it will switch immediatey, but since the sensor is so close, they will have to slow down then speed back up again, where they could keep their momentum up if they positioned the sensors further away. The solution to that would be to network all the sensor-based lights in an entire city, and use adaptive software to control them. It coudl tell what volume of traffic was passing through every intersection and respond accordingly from several blocks away. If that network went down, it would just default to normal behavior.

It depends on where the roundabouts are used. In areas of heavy congestion they do need to be part of an overall plan of traffic flow.

OTOH I've driven in the US (about 3k miles around California last November) and outside of the cities traffic is light enough for roundabouts. I also think (but I'm not a road designer) that your typical street layout ought to be ideal for roundabouts as there are usually several ways you can get to a destination by just taking a later or earlier street.

In the UK we do also use traffic lights so I'm not suggesting replacing all junctions. It just seemed silly that several times I had to stop at red lights when there was no traffic. Worse still is the multi-way stop. Those could (IMO) all be replaced by roundabouts.

But, hey, I'm not a road designer - was just a thought

By flashing at night I mean yellow flashing for the main road not the secondary road. That way, if you're on the main road you don't have to stop. Secondary road would have a red flashing light. Also, in 99% of all cases, the "in road" trip sensors are too close to the intersection so you always have to stop at the red before the light will change anyway. This makes no sense when there is absolutely no traffic.

Oh, that's why NASCAR uses so much fuel, they alway are turning left!

One of my professors had a rule against making left turns but his was due to being broadsided while taking a left. He would actually make 3 right turns instead of taking a left. He was a Traffic Engineering Professor.

The programming on traffic lights usually require the main road signal to turn red occasionally even when the sensor doesn't see any traffic on the side road. This is a form of fail safe in case of sensor failure and prevents a continuous red on the side road.

Rotaries aer being phased out in most places because they are unsafe, especially at higher speeds. The preferred solution on a major road is a flyover (grade separation) which allows the major move to continue without stopping. They are cost prohibitive in most cases so the next best solution is a signalized intersection. If I remember correctly, new traffic circles cannot be constructed in MA.

I agree about the flashing lights at night or at other times of low traffic. I work overnight shifts alot and it is maddening having to stop at a 30 second red light with no traffic in sight for half a mile - I run them routinely.

Boston actually has an adaptive, interconnected traffic signal system. The tough part is keeping it maintained and operational. Especially with brand new, multi-billion dollar tunnels closed due to falling ceilings.