Transportation System Plan 2018-2038

An intersection’ s v/c ratio and LOS are not directly proportional. A reasonably good LOS can accom pany a high v/c ratio provided that there is optim al signal progression for the higher-volum e movem ents at the intersection and relatively low m inor-s treet volum e. In this situation the m ajor-street traffic would experience m inimal delay at the expen se of the delay for the m inor-street traffic. The average delay for all m otorists would be relativel y low because of the low delay for the m ajor-street traffic. Conversely , a poor LOS may be experienced at an intersection with a v/c ratio less than 1.0 if the signal timing is not optim al. In these cases, som e of the intersection capacity is not used effectively or at all. Intersection v/c ratio does serve as a valuable indicator of potential problem s at intersections. Once the v/c ratio extends slightly beyond 1.0, LOS generally approaches F because vehicles m ust wait through multiple signal cy cles in order to pass through the intersection. In general, traffic facilities are analy zed for the worst fifteen-m inute period of the annual 30th-highest hour intersection volum e. The peak fifteen-m inute volum e is determ ined by dividing the 30th-highest hour traffic volum es by an applicable peak-hour factor. The peak-hour factor is defined as the 30th- highest hour volum e divided by four tim es the m aximum 15-m inute volum e during that hour. The peak- hour factor is alway s less than or equal to 1.00. Therefore, dividing the peak-hour volum e by the peak- hour factor results in an increase in design volum e. Fo r future y ear analy ses, a peak hour factor of 0.90 was assum ed for all m ovem ents, which is consistent w ith the City of Medford’ s current requirem ent for traffic im pact analy ses. Heavy vehicle percentages have a slight effect on intersection level of service and volum e-to-capacity ratios. For purposes of this analy sis, the PM Peak Hour heavy vehicle percentages were set at the SYNCHRO default value of 2 percent. Multi-hour LOS Assessment Methodology The principal purpose of the LOS study is to determ ine the list of projects that would be required over the planning horizon to m eet various LOS thresholds. Fo r purposes of this analy sis, three thresholds were considered – PM Peak Hour LOS D, PM Peak Hour LOS E, and two-hour PM Peak Hour LOS D. The first two thresholds were analy zed using direct level of service output from the 2023 PM Peak Hour SYNCHRO m odel that was developed for the project . The two-hour PM Peak Hour LOS D standard required som e further m odification to the 2023 SYNCHRO m odel in order to assess the projects that would be necessary to accom modate such a standard over the planning horizon. The two-hour PM Peak Hour LOS D standard basically allows intersections to operate at unacceptable levels during one hour of the day provided that a LO S D target is achieved during the second highest hour of the day. For purposes of this analy sis, the two- hour window of peak traffic was assum ed to occur from 4:00 to 6:00 PM. The peak one-hour period could occur during any part of this two-hour window. The second highest hour volum e was assum ed to be the total two-hour volum e between 4:00 and 6:00 PM, less the volum e during the peak one-hour period. Therefore, the second-highest hour volum e does not alway s represent a consecutive one-hour period, but is rather the “shoulders” of the two-hour volum e not encom passed by the true peak-hour volum e. In order to evaluate the operation during the second- highest hour, the 2002 counts were used to develop a volum e reduction factor that could be applied to the 2023 PM Peak Hour SYNCHRO m odel versus developing a new set of traffic volum es for the entire city . 2002 counts were provided from the City for the period from 4:00 to 6:00 PM. The counts were copied to a spreadsheet and the peak-hour volum es were subtracted from the two-hour volum e for each m ovement at each intersection. The total intersection volum e for the second-highest hour at the intersection was then divided by the peak-hour volum e at the intersection to obtain the volum e reduction factor. This factor was then applied to each m ovem ent at the G-5