Minimum Turning Radius requirements

[Roadbuilder]

I am designing a cul-de-sac with a 32 ft (16 ft radius), island in the center per my clients request. A Sanitary Sewer lift station is to be constructed inside the island. The outside radius of the island is 40 ft per the local code and standards. My concern is the minimum inside diameter turning radius required for emergency vehicles such as large ladder or pump trucks. I do not want to create a situation where the rear tires of emergency equipment would have to jump the curb and possibly damage the lift station in an emergency situation. I have not been able to find a lot of information on this subject so it may not really be an issue. Please provide comments/advice on this issue. Thanks in advance.

 

[bimr]

Your local fire marshall should be able to provide you with the necessary dimensions.

It is not just the turning radius of a specific vehicle. It is generally a municipal code requirement, which accomodates for the worst case scenario, in terms of what speed they might be travelling at, what new vehicles are expected in the future, how many vehicles might be expected to be there at a time, etc.

 

[MiketheEngineer]

I believe Auto Cad has a "plug-in" that will help and I am sure there are other cheaper software that will help.

BUT local code will be the ultimate law.

 

[TerryScan]

I took a stab at this configuration with Autoturn.
1. Keep in mind, even though a cul-de-sac is round, the typical fire turnaround manauver in one is a three-point turn, not driving in a circle.
2. The analysis will partially depend on the width of the normal roadway and the outer edge transition radii.

I put in a 20' approach road and 50' raddii on the transitions. To get the ladder truck we use around (driving in circle) it was extremely tight with a 40' outer radius, but I could make it happen after a few tries.

 

[ImroZ]

Hi,

By the standards of my country (Hungary) the required central radius is a 10 metres one in case of trucks. It is a correct number, I tried it (with truck).

BUT as I experienced there is no way to avoid the "accidents" you wrote about. I think the best you can do is the strenghtening the top of the station (the solution is depends on the structure of it).

If you need any kind of help, please send more information about the problem !

I hope it was useful.

 

[Debaser]

Could you use a kerb like this on the inner radius to prevent over-runs?

http://www.marshalls.co.uk/select/_data/productinfo/KERB01.pdf

 

[civilman72]

This sounds too tight for a standard ladder truck. It may be possible to manuever through the cul-de-sac with numerous three point turnarounds, but this will be unaccptable to the fire department for emergency access - they need to be able to drive through these turnarounds. I would recommend at least a 90' diameter, but (as stated above) you need to check with the fire district. It would not surprise me if their standards vary from the local road standards.

 

[CPENG78]

Roadbuilder,
I agree with many of the posts, it sounds like its too tight. I'm used to seeing minimum 45 ft radii. I don't know if increasing the readius of your curb is driven by right of way limitations or actuall physical obstructions. If this is not the case I would increase it, of course taking into account the fire marshal, municipal code and any other agency having jurisdiction.

Other options to consider and if its allowed by the local agency, is to provide mountable curbs on both your outer curb and your inner island curb. This would give the emergency vehicle an opportunity to mount the curb and sidewalk as necessary. If this is the case, you would have to consider your sidewalk structural section for the additional load.

By the way, I don't know if you have considered this but I'm assuming the your lift station footprint "fits" within your inner island. If there are any components above ground, you may want to consider installing bollards to protect that equipment from accidental impact. Hope this helps.

 

[TGLG]

Whether an inside radius of 16' is adequate really depends on what the outside radius will be. If the roadway is wide enough it should not be a problem.
That being said, also bear in mind that people parking on a cul-de-sac often park head-in/perpendicular rather than parallel to the curb, which can impact the useable width of your travel lane.

 

[chicopee]

refer to the PDF attachment. It is copied from the American Graphic Standard.

 

[Phidelt218]

I agree with all previous posts. Have you thought about incorporating drivable curbs and using something such as a bollard to project the lift station?