Corner Departure Sight Distance with On-Street Parking?

[raydefan]

An issue has come up a few times now which has really bugged me. Whenever a road has on-street parking, it appears that cars parked on the street are within the departure sight distance triangles (per AASHTO). For example, on a project that I'm working on with a 40 mph design speed, if you plot the departure sight distance triangles at a typical intersection, you would need to restrict parking for about 300' from the intersection which would be most of the block. Currently, cars are allowed to park up to about 20' from the intersection. I've research this a lot and the only thing I've found is to allow a certain distance from the crosswalk (20'-100', depending on the design speed), but this if really for the pedestrians to see approaching cars before they cross and not for the vehicles on the minor street. Is this something that is just an acceptable risk since on-street parking can be very desirable or is there something I'm missing? Any thoughts would be appreciated.

Thanks!

 

[bridgebuster]

I looked at the AASHTO Green Book, which I'm not an expert on, and my take is that departure sight distance is only applicable at railroad crossings. I also looked at the NYCDOT Street Design Manual but it doesn't address your concern. In NYC street parking is typically the length of the block from crosswalk to crosswalk. Although stop bars, which aren't everywhere, are 10' before the crosswalk.

Free parking is an amenity that makes politicians look good and metered parking is a source of revenue, which politicians also like. Perhaps in your case, 20' is the municipality's rule and it's probably based on accident history.

 

[ACtrafficengr]

Departure sight triangles are important for uncontrolled, yield, and two-way stop intersections. It's less of a factor at signals and all-way stops.

Because business lend a lot of (and possibly inflated) importance to parking availability, I'd eliminate parking spaces at intersections with higher than expected right-angle crash histories, and leave the rest alone.