Nifty Freeway Interchange Design
npr.org
npr.org
One of the most vexing aspects of traveling between mainland China and Hong Kong is the car travel: People in the former drive on the right side of the road; people in the latter drive on the left (a vestige of the British empire).
So to quell confusion at the border and, more importantly, to keep cars from smashing into each other, the Dutch firm NL Architects proposed a brilliant, simple solution, the Flipper bridge.
The most standard design (called A4 in the wikipedia article) has the same amount of traffic lights as this design. There is no driving on the left, no weaving, and there are no left turns with oncoming traffic.
Access onto the highway is a right turn for all directions. Access from the highway is light-controlled right or left turn. The highway has more capacity than the intersecting road, so while dumping traffic from the road onto the highway at a maximum rate using the easy right turns is fine, the light at the exit off the highway serves as rate limiter if necessary so that the road is not overwhelmed with traffic.
[1] http://www.inside-lane.com/wp-content/uploads/2009/11/Diverg...
It is pretty close to a cloverleaf interchange (http://en.wikipedia.org/wiki/Cloverleaf_interchange), but with the addition of stoplights on the road.
It seems that this will still suffer the weaving problem that plagues cloverleaf intersections - note how on the bridge cars first enter the road (from the freeway) and then shortly afterward, leave.
Perhaps this could be mitigated by placing stoplights on the offramps (which can be conveniently anti-synchronized with the lights controlling the bridge entrance), but I imagine space on the offramp could be a huge issue.
Makes it easier to understand, seeing it from above. I also suspect I have seen this on an infrastructure blog which I can't recall offhand.
Instant edit: Could the submitted title be made clearer?
edit: video of an example, around the Arc de Triomphe -> http://www.youtube.com/watch?v=lay8aZlsbB0
Your point is valid, but I (and others more qualified) argued this ends up being safer. People's mental model changes when they get to a roundabout, they sort of switch on their brain a bit more. I have in my head, but can't find a reference, that roundabouts are actually surprisingly safe.
Two-lane roundabouts are pretty dangerous, though -- while I've never had an accident in one I've always suspected that I might. And anything more than two just seems to be crazy.
And here is a direct link to the video (13MB): http://www.modot.mo.gov/springfield/major_projects/Greene/DD...
There are also some more pictures: http://www.modot.mo.gov/springfield/major_projects/Greene/Di...
In the left lane, people go fast. It's dangerous and difficult to merge from an exit ramp onto the left lane.
The roads that merge both have only one lane. The one that comes from the right has a yield sign. It also has a rather sharp bend just before the merge so 1) the cars are unlikely to go at high speeds, and 2) the drivers can easily see each other before the merge, so it's actually good design.
Also, something else caught my eye: City's name is Springfield, and the name of the woman that works at the gas station is Faith FLANDERS. :)
How long before traffic systems start broadcasting the schedule for the next minute or two so cars can plan ahead and always get there when the lights green?