Bodkin / Headford Road roundabout replacement [Lights are on!]

Iwannahurl

The way should be cleared for buses, pedestrians and cyclists to proceed, for obvious reasons.

But is there not some merit in creating gaps in general traffic?

Webbs

Iwannahurl wrote: »

The way should be cleared for buses, pedestrians and cyclists to proceed, for obvious reasons.

But is there not some merit in creating gaps in general traffic?

Why would you want to create gaps? At busy times surely the aim is to get the largest volume of traffic be it car bus or bike through a point in the least amount of time. All gaps do when there is a high volume is create bottlenecks further back in the traffic chain.

galwaycyclist

Webbs wrote: »

Why would you want to create gaps? At busy times surely the aim is to get the largest volume of traffic be it car bus or bike through a point in the least amount of time. All gaps do when there is a high volume is create bottlenecks further back in the traffic chain.

Hmm no not really it depends on what the limiting resource is in the system.

That was the problem with the roundabouts traffic just kept feeding into them until they lock up.

If you keep feeding everything forward regardless of the capacity ahead then you overload the downstream bottlenecks.

If you keep feeding in traffic beyond the capacity of downstream junctions to process it, then all you are doing is changing the location of the queues rather than necessarily reducing journey time. If you remove capacity (gaps) from cyclists or pedestrians in order to relocate queues of cars then you are creating pressure on those people to drive as well - which just adds to the problem.

Iwannahurl

https://www.youtube.com/watch?v=8G7ViTTuwno

Webbs

Iwannahurl wrote: »

https://www.youtube.com/watch?v=8G7ViTTuwno

Yip agrees with my point of getting maximum amount of traffic (rice) through a system in the least amount of time. How you do that is with a well designed system that allows a controlled flow of traffic with minimal interruptions.
Galway council is a disaster when it comes to using alternative means of coping with pedestrians and cyclists such as overpasses, underpasses etc

Iwannahurl

Your point was:

Webbs wrote: »

Why would you want to create gaps?

There are various ways of creating 'gaps' in traffic, and of maximising throughput (of people, not just automobiles).

galwaycyclist wrote: »

If you remove capacity (gaps) from cyclists or pedestrians in order to relocate queues of cars then you are creating pressure on those people to drive as well - which just adds to the problem.

Unfortunately in Galway there is a lot of racing to the next traffic jam. The Bodkin roundabout was clogged because there was no way to create gaps for traffic to filter through at a more efficient pace. Properly configured traffic signals, linked to a UTC system, should be achieving what is illustrated in the video. But not at the expense of pedestrians, cyclists and bus users.

antoobrien

Iwannahurl wrote: »

Properly configured traffic signals, linked to a UTC system, should be achieving what is illustrated in the video. But not at the expense of pedestrians, cyclists and bus users.

Actually the video is demonstrating a dissimilar scenario - roads like the I95 and beltway around Washington DC - which have grade separated junctions rather at grade junctions (i.e. lights, roundabouts, etc.) where one doesn't have to stop to let somebody else one.

If one wants to accurately simulate the N6 in Galway one would have to stop the flow through the funnel simulating the effect of the traffic lights.

Iwannahurl

antoobrien wrote: »

Actually the video is demonstrating a dissimilar scenario - roads like the I95 and beltway around Washington DC - which have grade separated junctions rather at grade junctions (i.e. lights, roundabouts, etc.) where one doesn't have to stop to let somebody else one.

If one wants to accurately simulate the N6 in Galway one would have to stop the flow through the funnel simulating the effect of the traffic lights.

And yet DC's "infamous" Capital Beltway is "synonymous with traffic jams". See below. The root of the problem is self-evident, and ultimately it's not about stuff like grade separation, which the USA has in abundance compared to Ireland.

It’s been 50 years since the Capital Beltway looped its way into the heart of the Washington area. The 64-mile highway is synonymous today with traffic jams.

A Not-So-Happy Hour?

Drivers were ecstatic during the Beltway’s first few months of operation. Destinations that could once only be reached via narrow, slow roads were now accessible by this massive and quick-moving highway. Newspapers ran letters from commuters praising the new road. Korr says there was even a possibly apocryphal story from this time that said local bars were losing business because workers could no longer tell their wives they’d been stuck in traffic when they were really grabbing a drink. But the Beltway’s problems soon became apparent.

5 Minutes
The time it took for the first traffic jam to form on the Beltway after it opened. A crowd of thousands had gathered for the inaugural ceremony, then dashed to their cars as soon as the ribbon was cut. This caused a two-mile-long jam at the New Hampshire Avenue interchange in Hillandale that took 20 minutes to clear—an ominous sign of the road’s future.



55,000
The number of vehicles per day Maryland traffic officials expected to use that state’s portion of the Beltway.

1 Year
Time it took to top that estimate. Further increases in traffic rose much sharper than engineers predicted. Today the busiest sections of the Beltway can average 200,000 to 225,000 vehicles a day.

15 Months
Time it took after the Beltway’s opening for the American Automobile Asssociation to convene a forum titled “Golden Ring or Vicious Circle?” to debate whether the highway lived up to its promise or was already doomed to failure.

http://www.washingtonian.com/articles/people/the-beltway-turns-50-stuff-you-didnt-know-about-washingtons-infamous-road/

biko

Head over to Infrastructure guys. This bar is now closed.