28

As others stated before, induction loops are the primary - most reliable method: the coils (usually just several loops of wire) embedded in the road; fed given frequency from a generator, in presence of metal the frequency of the LC circuit changes and the sensor circuitry detects the change of frequency, producing a presence signal. In some cases these may ...


27

I think you are talking about roundabouts, not traffic circles. It is baffling to those of us in the UK that Americans think roundabouts are a new idea. In the UK we have so many variants, from mini-roundabouts all the way up to full motorway junctions (a giant roundabout above or below the motorway). So do roundabouts take up more space? Not necessarily, ...


14

There's a hierarchy of junctions, that you'll find in most standard highway design guides, such as the UK's immense Design Manual for Roads and Bridges. Different junction designs have different motor-vehicle capacities, and operate best at different speeds. Within towns and cities, junction capacity is critical: it is that that determines the network's ...


13

There are two techniques commonly in use. The first is induction loops cut into the road surface. The metal in a vehicle body induces a current in the loop, as the vehicle passes over it. (public domain pic from wikipedia) The other is cameras / radar (either Doppler microwave for moving vehicles, or infra-red for static vehicles at the stop line), ...


11

Roundabout: Pros As you've mentioned, the Mythbusters' test results showed that roundabouts were about 20% more efficient for cars, good for high traffic Allows more cars to cross at a time. Doesn't need traffic lights. Safer Cons As you've also mentioned, it takes up more space. Uses more material to make. 4-way intersection Pros Easier for ...


8

Like the British, Australia has had roundabouts for at least five decades in some shape or form and there prevalence has increased over the last thirty years or so. In the city were I live there is a five-way intersection and it is controlled by a single roundabout, nothing else. It's been operating for at least forty years without any issues. It's easier ...


6

The answer is slightly more complex than what the OP proposes -- this is due to two factors: The interconnect must be fail safe -- i.e. if the interconnect circuit fails, the system must be able to detect this and report a problem to both highway and railroad maintenance crews. To this end, special supervised circuits are used, using two relays in opposite ...


6

Roundabouts are only good for equal distribution of incoming traffic. As soon as one road feeds more traffic it will starve the other roads. Small roundabouts are less efficient than large ones. So to get an efficient roundabout you need some space to lay it. Mini's are only good to specify equal right of way to the roads in low traffic areas. Double lane ...


5

The induction loop is the most reliable for switching on demand. Though it has the down side that motorcycles are more difficult to detect because they have less metal to detect. a similar issue exists for carbon fiber cars. Radar is typically only used to extend the green times as it can only detect moving vehicles reliably. Some intersections use a ...


4

People using the road make mistakes (like running stop signs and red lights), always have and always will. Crashes will always be with us, but they need not result in fatalities or serious injury. Modern roundabouts are the safest form of intersection in the world - the intersection type with the lowest risk of fatal or serious injury crashes - (much more ...


3

This will be done with a video camera. Writing software to process images is easier than it used to be. People are writing software on Raspberry pi (and I think, impressively, even Arduino) that do this sort of thing. And given that your application is a driverless car, it would need similar capabilities anyway. MATLAB software is actually capable of ...


3

This answer is based on personal observation and commonsense. There is little science but some engineering intuition. I don't claim any civil or traffic engineering expertise. Like most engineering solution no one size fits all. Traffic Circle (Round about) Traffic Circles are good for areas with low traffic volume, warm climate and with large population ...


3

What country? This is different between different countries. I can give the sequence in Poland, which is standard in most of EU. 180 seconds of Blinking Yellow. (Groups [**] with Yellow blink yellow, the rest remains off. If the controller was already in this mode, past duration is counted towards the 180 seconds.) All Yellow. Whichever groups don't have ...


1

There is another state the lights can be in: blinking yellow. Which means that the intersection is not being controlled and normal priority rules are in force. Going from off to all blinking does not change how you should behave on the intersection. Going from blinking yellow to solid yellow (longer than the normal 3 seconds) to red gives drivers enough ...


1

As you might well imagine, there is a metric f-ton (the technical term :-) ) of research covering both queuing theory and prioritization analysis. The correct, if unsatisfying answer to your title question is: there is never acase where two items have exactly equal priority, just as in American baseball there's never an exact tie between ball reaching ...


1

The state of any traffic lights is just one of the many elements that are extracted from the scene in front of the vehicle using video cameras and machine vision. Software identifies objects such as other vehicles, pedestrians and other potential obstacles, plus information such as road edges, lane markings, signs and traffic signals.


1

Roundabouts let traffic flow more smoothly and there is also less reliance on technology that can malfunction due to a series of factors (i.e. power outage, etc).


1

In any design regarding public traffic your biggest problem is going to be managing the human factors of competence, confidence and error. The entire purpose of traffic management is to control human behaviour. With automated traffic it is simply an issue of coordination but humans are not well coordinated. Some are slow, others are nervous, other people are ...


1

Something that I didn't see mentioned here is a HUGE saving in wasted fuel, burnt by cars and truck sitting at a traditional intersection, waiting for a light to change. To me, this is the best feature. Roundabouts are planet friendly period! Another spinoff to this is the reduced frustration to drivers who are sitting, waiting and waiting and waiting...


1

Most of the pros regarding a traffic circle have been touched on here. It's also worth mentioning that traffic circles, despite their efficiency in decreasing accidents in heavily-congested areas, are truly harrowing -- often fatal -- for the blind & impaired. Long, R. G., Guth, D. A., Ashmead, D. H., Emerson, R. W., & Ponchillia, P. E. (2005). ...


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