Interstate Standards

[Mergingtraffic]

Anybody have a list of all the interstate standards there are?

[J N Winkler]

http://en.wikipedia.org/wiki/Interstate_highway_standards

[vdeane]

What exactly defines median width?  It looks like there might be sections of I-86 (including the Corning and Horseheads bypasses) that don't meet interstate standards, as well as a couple of bridges near Campbell that definitely don't.  I wonder why these were allowed when the feds are being so strict with the quickway.

[Quillz]

Was it grandfathered in?

[J N Winkler]

What exactly defines median width?  It looks like there might be sections of I-86 (including the Corning and Horseheads bypasses) that don't meet interstate standards, as well as a couple of bridges near Campbell that definitely don't.  I wonder why these were allowed when the feds are being so strict with the quickway.

I don't trust what the Wikipedia article says about median width, to be honest.  It looks like it was taken straight from one of John Lansford's posts to MTR and I can't tell whether the median criteria values are for "grass width" or for actual median width, which from an engineering standpoint is always measured ETW to ETW (i.e., from the left shoulder stripe in the "up" direction to the left shoulder stripe in the "down" direction).  True median width includes the width of the left shoulders, while "grass width" is basically true median width minus the widths of the left shoulders.  10' minimum median width in urban areas and mountains sounds about right for true median width because that includes 4' left shoulders with 2' left over for center Jersey barrier.  36' minimum width for rural areas sounds too low.  In Kansas 60' is the usual width for rural medians, and other states have shifted to 70' or even more.

[vdeane]

Was it grandfathered in?

If they were going to grandfather in NY 17, why do it just for the portion west of the Chemung county line and not everything that didn't have at-grade intersections.

What exactly defines median width?  It looks like there might be sections of I-86 (including the Corning and Horseheads bypasses) that don't meet interstate standards, as well as a couple of bridges near Campbell that definitely don't.  I wonder why these were allowed when the feds are being so strict with the quickway.

I don't trust what the Wikipedia article says about median width, to be honest.  It looks like it was taken straight from one of John Lansford's posts to MTR and I can't tell whether the median criteria values are for "grass width" or for actual median width, which from an engineering standpoint is always measured ETW to ETW (i.e., from the left shoulder stripe in the "up" direction to the left shoulder stripe in the "down" direction).  True median width includes the width of the left shoulders, while "grass width" is basically true median width minus the widths of the left shoulders.  10' minimum median width in urban areas and mountains sounds about right for true median width because that includes 4' left shoulders with 2' left over for center Jersey barrier.  36' minimum width for rural areas sounds too low.  In Kansas 60' is the usual width for rural medians, and other states have shifted to 70' or even more.

True median width sounds right - these bypasses are mostly valid in this case (there is some sub-standard right shoulder on the Corning bypass and on bridges).