COM 0590.000 2010-2012 - Laserfiche WebLink

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� ' •William P. Kenoi % +:R!`"�'%��'+% Warren H.W. Lee Mayor _ Director • William T.Takaba Brandon A. K.Gonzalez Managing Director Deputy Director Couttti of Paimil DEPARTMENT OF PUBLIC WORKS Aupuni Center 101 Pauahi Street,Suite 7•Hilo,Hawai`i 96720-4224 (808)961-8321 •Fax(808)961-8630 www.co.hawaii.hi.us February 1, 2012 TO: File SUBJECT: ONE LANE BRIDGE SIGHT DISTANCE STUDY FOR YIELD LOCATION Kalopa Road bridge fronting parcels 4-4-2:5, 4-4-2:6, 4-4-9:3, and 4-4-9:8 BACKGROUND INFO: Per the Manual on Uniform Traffic Control Devices (MUTCD), "The YIELD sign assigns right-of-way to traffic on certain approaches to an intersection. Vehicles controlled by a YIELD sign need to slow down to a speed that is reasonable for the existing conditions or stop when necessary to avoid conflicting traffic." The use of a yield sign would be appropriate on a one lane bridge because a full stop is not always required and would give clear indication as to who has the right-of-way should two-way traffic approach the bridge at the same time. ONE LANE BRIDGE STUDY DATA: Prior to assigning right-of-way on a one-lane bridge, there are two sight distance measurements that Traffic Division verifies and studies. These measurements help to determine which side would be best for the yield condition. The first sight distance check is the stopping sight distance for a yield condition. This would be the distance required by each driver to see an oncoming car to allow the driver to stop prior to entering onto the bridge. For the 25 mph hour case, this stopping sight distance would be 115'. The total distance a driver would need to see across would be d1=115'+length of bridge+115'. See detail 1 — sight distance check #1 for more info. The second sight distance check is the sight distance needed for a driver at the yield bar to safely clear the bridge. We base this on timed samples of drivers going across the bridge at a safe speed. The formula for this distance is d2=1.47*(time to cross bridge)*25 mph+bridge length. For the subject bridge, the sight distance would be d2=1.47*(9 sec.)*(25 mph) = 330.75'+bridge length. See detail 1 — sight distance check #2 for more info. County of Hawai`i is an Equal Opportunity Provider and Employer.