Traffic signals at interchanges

[Tom89t]

Traffic signals at freeways interchanges  are good but, can cause problems because the two interchanges can back up traffic that is exiting on to the street. I think the SPUI interchange would work better  because there  only   one intersection to go through.

[InterstateNG]

Good to know.

[jwolfer]

Traffic signals at freeways interchanges  are good but, can cause problems because the two interchanges can back up traffic that is exiting on to the street. I think the SPUI interchange would work better  because there  only   one intersection to go through.

depends on traffic volume. SPUIs are cool for many places there are a few around Jacksonville now

[Kacie Jane]

Traffic signals at freeways interchanges  are good but, can cause problems because the two interchanges can back up traffic that is exiting on to the street. I think the SPUI interchange would work better  because there  only   one intersection to go through.

depends on traffic volume. SPUIs are cool for many places there are a few around Jacksonville now

This.

Just like any other construction project (i.e. widening), there's an evolution involved as traffic counts go up.
1. Basic diamond with stop signs.
2. Basic diamond with signals.
3. Either parclo or SPUI.

Of course, the major problem is the amount of construction require to go from #2 to #3.

[roadman65]

I-4 and Lee Road is a diamond with problems due to 2 separate signals.  Agree, SPUI work the best!

However major construction would be needed here.  If someone would show Orange County, FL officials how to time traffic lights, it may improve some of the problem here.  Unfortunatley, the county I live in can not figure out how to time and place signals if their own lives depended on it.

[roadfro]

Traffic signals at freeways interchanges  are good but, can cause problems because the two interchanges can back up traffic that is exiting on to the street. I think the SPUI interchange would work better  because there  only   one intersection to go through.

Problems at a signalized diamond interchange can be greatly mitigated by proper signal timing. Specifically, implementing diamond interchange signal phasing. If done properly, there are fewer stops in the middle and, depending on the situation, might also reduce wait times on the off ramp.

Just like any other construction project (i.e. widening), there's an evolution involved as traffic counts go up.
1. Basic diamond with stop signs.
2. Basic diamond with signals.
3. Either parclo or SPUI.

The consideration of a SPUI isn't one always based primarily on traffic volumes. Many times, SPUIs are selected for the smaller right of way footprint where a traditional diamond would be less feasible or acquiring right of way would be more costly.

[kphoger]

Multilane dumbbell interchange.   

[intelati49]

Traffic signals at freeways interchanges  are good but, can cause problems because the two interchanges can back up traffic that is exiting on to the street. I think the SPUI interchange would work better  because there  only   one intersection to go through.

depends on traffic volume. SPUIs are cool for many places there are a few around Jacksonville now

This.

Just like any other construction project (i.e. widening), there's an evolution involved as traffic counts go up.
1. Basic diamond with stop signs.
2. Basic diamond with signals.
3. Either parclo or SPUI.

Of course, the major problem is the amount of construction require to go from #2 to #3.

Actually, MODot's DDI is a solution to the SPUI problem. Millions cheaper than building a SPUI.

[Kacie Jane]

Just like any other construction project (i.e. widening), there's an evolution involved as traffic counts go up.
1. Basic diamond with stop signs.
2. Basic diamond with signals.
3. Either parclo or SPUI.

The consideration of a SPUI isn't one always based primarily on traffic volumes. Many times, SPUIs are selected for the smaller right of way footprint where a traditional diamond would be less feasible or acquiring right of way would be more costly.

I'm not following you here.  What do you mean by less feasible?  The only reason I can think of that a traditional diamond would be less feasible would be if the traffic volumes were high enough to cause bottlenecks between the two ramps.

[roadfro]

Actually, MODot's DDI is a solution to the SPUI problem. Millions cheaper than building a SPUI.

A Diverging Diamond Interchange (DDI) can be a good solution, and one of the benefits is each ramp intersection has only 2-phase signals. I'm not so sure how the DDI stacks up with other solutions for really high volume interchanges, though.

The consideration of a SPUI isn't one always based primarily on traffic volumes. Many times, SPUIs are selected for the smaller right of way footprint where a traditional diamond would be less feasible or acquiring right of way would be more costly.

I'm not following you here.  What do you mean by less feasible?  The only reason I can think of that a traditional diamond would be less feasible would be if the traffic volumes were high enough to cause bottlenecks between the two ramps.

My main thought was about right of way concerns, as there is a minimum and recommended spacing suggested between ramp terminals at diamond interchanges. If it would take too much ROW on either side to make that spacing fit, a SPUI can be an alternative.

Tighter diamonds (intersections spaced closely together) may not necessarily work well if turning volumes at the cross road are high and there is not adequate storage between the signals...in this type of case, a SPUI probably is better.

[mgk920]

Don't forget the option of 'dogbone' roundabouts, too.  There is an interchange here in the Appleton area (US 41/Breezewood Ln-Bell St, Interchange 129, in Neenah, WI) that was always a pain to use - it was always backing up with street traffic congestion, even during the late-night hours, with its heavy traffic and multiple major turn movements, on and off both US 41 and the two close-in frontage roads.  After its rebuilding last year, replacing those four signalized intersection with roundabouts, it's like 'where did all of that traffic go?' - it carries the same street traffic volumes, but it now drives like there is hardly any traffic at all there.

Mike