Cul-de-Sac and road extension question

[Wylie77]

We have a proposal in front of us that would take a current Cul-de-Sac and extend the roadway to the back of it. The proposal would keep the center island in tact, thereby creating a round-a-bout situation. While I have read many of the threads that it will promote a "traffic calming" effect. The roadway is only 20mph. The distance from the nearest intersection is approx. 275'.

Is there anyone out there that has had a similar situation. I am concerned with:
The amount of signage that I forsee being needed to warn drivers of the upcoming island.

Snow storage in the middle of the island and how it relates to vision obstruction.

Parking within the round-a-bout area itself.

I am presently opposed to the idea, because of the maintenance and liability concerns above. I am looking to either change my opinion based on unbiased comments or to solidify my opinion based on unbiased comments.

Thanks in advance for any ideas or thoughts.

 

[GeoPaveTraffic]

Round-a-bouts can have some traffic calming effect and can also "breakup" a street creating a more residential feel. If the cul-de-sac was to be converted then the resulting round-a-bout should conform to the recommendations in "Roundabouts: An Informational Guide". This guide also details the signage that should be installed.

One of the items that may cause the most trouble, and result in not making a round-a-bout, is the installation of spliter islands.

With respect to your comment about snow blocking sight distance. To create a traffic calming effect the sight distance needs to be blocked so people cannot see past the round-a-bout.

 

[Wylie77]

Where do I find the guide? I do understand and agree that this is a useful tool to calm traffic. As Director of Public Works I am looking at this from a maintenance standpoint, and how it is going to affect our operations. In particular in snow removal operations.

The proposal before the board would take an existing Cul-de-Sac and convert it to a round-a-bout. The approaching road is 28' wide, the roadway on either side of the island is 28' and the proposed continuing road is 28'. This configuration gives me 56' of roadway to plow in this short space. This will require additional time to plow. Additionally, our practice for Cul-de-Sacs is to plow the snow to the middle and place it on the island itself. Sometimes the pile of snow can get quite high. We try to remove it when time allows but sometimes it cannot be done. Another factor to consider is that a pile of snow is a kid magnet. We would now be creating a great liability with this in my opinion.

 

[GeoPaveTraffic]

The guide is published by the FHWA, I'm not sure where it is currently available. As for the snow, we generally plow to the outside of the cul-de-sac, but I see your point.

 

[ACtrafficengr]

Go to the FHWA website and do a Search for "Roundabouts: An Informational Guide" It's downloadable as pdf's.

One thing to be concerned about is make sure you are not creating a "rat run." If the new road will create a short cut between two connectors or arterials, or between a major road and a traffic generator, you may want to look for ways to slow or divert traffic.

How many new connections are being added to the cul-de sac? Will it be opposite or at an angle to the existing approach? Perhaps you could scarify one side of it to create a chicane. It might avoid some of the problems you're expecting, and still have a slowing effect.

 

[trafficPro]

How far is the road to be extended?
What is the new end condition to be vis a vis u-turns?
Who maintains the island?
Can fire trucks get past it easily?
What is the ROW situation? Quite often the cul reaches the end line with the circle tangent to the end line at one point only. That means land taking to extend the road. will snow storage destroy what ever landscaping is placed there?

If roadway is 20 mph now, at end of cul, what is need for traffic calming?
Check vertical profile. Often profile into end cul is OK for end of road, but not so good for continuation.

We have bad vibes for municipal cul center islands, and only permit them in private communities where they do the
maintenance.
TrafficPro