Roadside Cafe Seating 1

[TOHSEngineer]

What kind of clear zone guidlines are there for roadside seating at a cafe? We have a 25mph posted speed limit with vertical curb face with a 12' sidewalk on the back of curb. Can we have seating on the 12' sidewalk? AASHTO says to keep a minimum of 18" from the face of the curb for clear zone but I am feeling uneasy about this. Any suggestions? Thank you for the help in advance.

 

[IRstuff]

Don't you need to have at least a walkable section of the sidewalk?

TTFN
faq731-376

 

[ACtrafficengr]

If "TOHS" stands for "Town of...," and you are the permitting or reviewing engineer, I'm assuming you're wanting to cover your bases before saying yes. Look at it this way: people walk on the sidewalk all the time. How often do they get hit by vehicles?

IR's right, you need to keep an accessible route open. Say 3' for utility poles, signs, etc, and a 5 ft accessible route. That leaves 4' for tables.

How well do drivers obey the speed limit? How wide is the street? If any vehicle encroachment is likely to be low speed and low angle, I'd be fairly comfortable.

On a wide street, with higher speeds and vehicles potentially veering across the road and hitting the curb at a higher angle, there are greater chances of a vehicle hitting the diners.

Take a look at the crash history. If there are a lot of people striking the curb in the area, it may not be a good idea. If speeds are low and there is no adverse safety history, it might be a good addition to the neighborhood.

 

[IRstuff]

I've seen sidewalks narrower that cited here, but the minimum width of usable sidewalk is probably dictated by the requirements of the ADA, which apparently requires a minimum width of 36 inches:

http://www.ehow.com/about_5561359_ada-standards-sidewalks.html

http://www.ada.gov/pcatoolkit/chap6toolkit.htm#fn3

TTFN
faq731-376

 

[TerryScan]

"The difference between a "clear zone" and horizontal clearance or "operational offset" has been a topic of much confusion. When the Green Book and the Roadside Design Guide were last updated, the AASHTO committees coordinated to dispel the misunderstanding that 2 feet (actually, 18 inches) behind a curb constituted a clear zone. Since curbs are now generally recognized as having no significant containment or redirection capability, clear zone should be based on traffic volumes and speeds, both without and with a curb. Realizing that there are still contradictory passages in various AASHTO documents, the Technical Committee on Roadside Safety has initiated a short-term project to identify all such inconsistencies and to recommend appropriate language corrections. This effort is underway. The fourth paragraph under Section 3.4.1 Curbs in the 2002 Roadside Design Guide correctly defines AASHTO's "position"."

http://www.fhwa.dot.gov/programadmin/clearzone.cfm

So, the clear zone would at least be 7ft. from the travel lane (up to 16 ft. depending on ADT etc). Is there delineated parking or shoulder on the street? If so, the clear zone may fall within that area.

 

[ACtrafficengr]

IR, 36" is the minimum allowed width for an accessible route where 60" is not achievable. In this case, the width of the accessible route would be affected by the choice of tables. If this were on one of the roads my department maintains, I'd insist on a 60" accessible route, preferably 72".

My understanding of the 18" offset between the face of curb and fixed objects is more so people can open car doors, rear view mirrors don't strike the objects, and similar practical matters, rather than safety.

As TerryScan said, a standard height curb will rarely redirect a vehicle. When it does, it's often the left side tires that actually get redirected.