Turn lane length reduction
Turn lane length reduction
(OP)
Here is the situation.
Posted Speed = 25 mph
Design Speed = 25 mph + 5 mph = 30 mph
Min. Deceleration length (based on local agency manual for 35 mph Design Speed)= 145'
Queue Length = 50 feet
Total right turn lane length = 145'+ 50' = 195'
Available length = 110'due to constraints.
Difference = 85'
How can we justify reduction of 85' in total turn lane length. The roadway has no major crash history, no safety issues. Appreciate any help with this.
Posted Speed = 25 mph
Design Speed = 25 mph + 5 mph = 30 mph
Min. Deceleration length (based on local agency manual for 35 mph Design Speed)= 145'
Queue Length = 50 feet
Total right turn lane length = 145'+ 50' = 195'
Available length = 110'due to constraints.
Difference = 85'
How can we justify reduction of 85' in total turn lane length. The roadway has no major crash history, no safety issues. Appreciate any help with this.





RE: Turn lane length reduction
Does the 110' include taper length constraints?
Is 50' queue length based on an intersection analysis, or minimum req'd by local agency manual?
RE: Turn lane length reduction
TTFN

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RE: Turn lane length reduction
Whart is the AADT? Can you use AASHTO's Guidelines for Geometric Design of Very Low Volume Roads (<400 vpd)?
RE: Turn lane length reduction
110' includes a 50' taper
50' storage is based on intersection analysis (95th percentile back of queue)
This is an existing turn lane
There is no posted speed limit, so we were requested to use 25 mph as posted speed.
AADT=2000 VPD
RE: Turn lane length reduction
What are the turn lane length requirements for a 25 MPH design speed? Maybe using a 35 MPH design speed is excessive, particularly considering this is existing with little safety concerns/incidents.