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Protecting Vehicles from falling off wall.

Protecting Vehicles from falling off wall.

Protecting Vehicles from falling off wall.

Okay Engineering types,  I have a large parking lot which is bordered at one end by a 16 foot tall Keystone type wall.  The top of the wall is at parking lot level(parking lot is on fill).  The edge of the wall is 4 feet behind a 6" tall by curb.  I have about 100 feet I need to protect.  The vehicles are mainly semi-tractor trailers with lots of turning movements in this area.  Plus it is down hill from truck parking to wall at a 5% grade.  My first thought was a standard CalTrans Guard rail.  Then I started wondering if there are more economical methods...Any suggestions?  Maybe a tall curb? But how tall?

Thank you.

RE: Protecting Vehicles from falling off wall.

About 6 feet!!

RE: Protecting Vehicles from falling off wall.

Agree with Mike!  This is a true barrier condition.  You need to provide a barrier that complies with code...in this case a significant barrier.

RE: Protecting Vehicles from falling off wall.

This is in a parking lot, so assumed low speeds.  Under certain circumstances the existing curb at very low speeds can be a barrier.  If the speeds are high enough the existing curb could be a detriment - it depends on the angle of impact.

For only 100' of protection, in place of guardrail it could be cheaper to go with some form of a concrete (Jersey) barrier.

RE: Protecting Vehicles from falling off wall.

I was joking a bit - but something quite substantial should be used.  Remember the little old lady who hits the accelerator instead of the brake.

I would kind of like to stop her.

An out of control 18 wheeler - good luck

RE: Protecting Vehicles from falling off wall.

k-rail and anchor it down

RE: Protecting Vehicles from falling off wall.

Embed sharpened 10 foot long horizontal 4" XXS pipe in the wall on a 2 foot grid.  

If anyone dares to hit the wall, they won't leave.

Mike McCann
MMC Engineering

RE: Protecting Vehicles from falling off wall.

  Dig  a twenty foot wide trench  about  eight feet deep. once the front wheels of the eighteen wheeler hit that, I cant see it having enough kinetic energy to  keep going horizontally.

RE: Protecting Vehicles from falling off wall.

I don't think the Jersey barriers will help because they are designed to realign off course vehicles back on track. 12" steel posts filled with concrete and with enough embedment, spaced 4' apart, layed out about 10' from the edge and painted yellow with reflective tape should be satifactory.

RE: Protecting Vehicles from falling off wall.


Containment kerb is not really meant to be hit square on, but the 300mm/12" upstand should at least give an indication to a driver there was some hazard behind him him if he hit it. Paint it alternately yellow and black and there's a visual deterrent too. However, this would still need some sort of parapet to stop 'determined' drivers.

RE: Protecting Vehicles from falling off wall.

I've seen situations in which a curb was installed in front of a guiderail and the vertical motion imparted by striking (and jumping) the curb was sufficient to cause a car to vault up over the guiderail, so it is important to look at the distance between them.  The Pennsylvania DOT suggests placing the guiderail at the curb face or at least 12' behind it, but not anywhere between.

Bear in mind, also, that tractor trailers have big tires, and a 6" curb might not be much of a barrier to a truck.  I'd suggest something much taller, like 12"


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