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NCHRP Report 665 Question

State AZ
Description Text

Can you please confirm a couple of items regarding Table 89 in NCHRP Report 665.  We have been waiting for the AASHTO Roadside Safety Committee to adopt Dean's recommendations for some time now.  Please confirm the following:


1.      We use a design speed of 75mph for freeways that are signed for 75mph -  according to the text we can use the 70mph design speed in Table 89 for 70mph and higher.  We will label the Design Speed column as 70mph and higher.

2.      We use 65 mph design speed for urban freeway design.  Interpolate between the 60-70 mph values in the table.

Other Keywords NCHRP Report 665
Date January 20, 2011


I conversed with Dr.
Sicking about the use of interpolation with Table 89 of
NCHRP Report 665. He confirmed
that the use of the 70 mph design speed
runout lengths would be acceptable for use on roadways with speeds of 75 mph, and the 70 mph speed limit may be referred to as 70 mph and higher. He also
confirmed that interpolation between the 60-70 mph range for
runout length design on roads with speed limits of 65 mph would be acceptable.

Date February 3, 2011

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