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Re: Design of bollards

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ASQUILALA(--nospam--at) wrote:

> I think some of our list members misundertood the above statement.  My
> understanding is that speed bumps are placed before the bollard to slow down
> the vehicle before hitting the bollards.  This is the proper way to make sure
> that the vehicle will not hit the bollard at top speed.
> Placing only speed bumps instead of bollards will definitely won't gonna
> work.

As I understand several of the post, people are questioning whether using speed
bumps to limit the speed at which a vehicle can hit a bollard is effective, since
vehicles can cross speed bumps at very high speeds if damage to the vehicle is
not an issue.  A speed bump may be sufficient to limit the speed if your concern
about the bollard capacity is mainly for minor accidents and superficial damage
to a building exterior (such as a fast food drive through), but a speed bump
probably does not help reduce the speed of impact if you are concerned about
deliberate acts of violence or high speeds accidents in general.  If life safety
is the issue, it might be advisable to design the bollard for a high speed
impact, regardless of the presence of speed bumps.  If the bollard cannot
tolerate such impacts, there are many option, such as jersey barriers, large
planters, etc.  The massive concrete flower planters springing up around
government buildings around the country aren't just for looks, after all.
Forcing a vehicle to make a right angle turn immediately before approaching
whatever your don't want to get hit is also effective (assuming the approach is
sufficiently limited that a vehicle can't just come straight at the location some
other way, like across a lawn), since the speed that a vehicle can negotiate a
sharp turn is limited.  That approach has been used in front gate designs since
Biblical times (since sharp turns also slow down unruly mobs and charging armies)
and is evident in fast food drive throughs.  Even in small spaces, speeds can get
very high, so it pays to be careful.  A vehicle in a parking garage near my
office went out of control last year (driver had a heart attack) and hit a
concrete column at an estimated 70 mph.  I wouldn't have guessed that you could
get up to 70 mph in a parking garage straight-away.  It was a big car, too, and
managed to put some large cracks in the column.