Intersection Design? 1

[lucky12345]

Hello,
I am looking for information on offset intersections. The situation is that I have a main thrue highway and crossing roads centerlines are about 15m offset. I need to prove that the signalized intersection is either safe or unsafe for turning movements. Existing reg's?

Thanks!

 

[dicksewerrat]

Rebuild the crossings to make them coincide. Sound like the surveyor lost his transit and just followed the two cowpaths to the main road.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[zabrab]

I have to agree with dicksewerrat; if possible try to align the two minor approaches to form a more conventional four-leg intersection. That would only be a realignment of 7.5 m (25 ft) for each road. If that is not possible, the safest way to operate the signal would be, in all probability, to run the minor approaches individually(assuming traffic volumes are such that you can run a split phase in your cycle length).

 

[ACtrafficengr]

Does the intersection look like A: or B:
| |
______|______ ____|________
| |
| |

Intersections like A tend to have more problems, although concurrent phasing can be confusing for both. It's hard to tell what the other driver's intentions are.

If you can get a "B" setup with an offset of more than 200'or so, you are golden. You can run them as two three-leg intersections, and you don't need left-turn storage between the intersections. Sideraod through traffic doesn't get stuck on the main road waiting for a gap for a left turn.

ROW costs are likely to be higher than Zabrab's suggestion, but you may get safety and operational benefits. Unsignalized, it will be safer than a 4-leg.

------------------------------------------
"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail."

Wm. Phelps Eno, ca. 1928

 

[rgsdez]

Just a thought, try connecting the side roads and mainline with a Roundabout.

 

[kxa]

I had a situation like this and ended up making it a a 4-leg intersection. If you have to have it this way, maybe you can restrict some of the turns or make them one-way streets to minimize the conflicting movements. This is a good idea if you have adjacent intersections that the drivers can go to to make the turns onto the main road.