pages: TransportationCommission/2009-04-22.pdf, 5
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TransportationCommission | 2009-04-22 | 5 | DRAFT last Commission meeting, that this would be put on hold pending further discussion of the relationship of intersection to segment analysis. Staff Khan stated there was a question at the last meeting as to why intersection LOS for autos be maintained and having urban street LOS also be provided. Dowling & Associates' response was when looking at intersections it was very critical to have an understanding of what was happening at the intersections in terms of turning movements. When the urban street LOS was calculated, it only looked at autos going straight. When intersection LOS is considered, left turns had to be reduced significantly to provide more time for pedestrians to cross, this caused the queues spilling out from the left turn pockets that were impacting the through movement. The Police and Fire departments indicated their concern about the impacts to emergency response times. He wanted to clarify that by having this intersection level of service allowed us understanding not just about autos, but pedestrian, bicycle and transit improvements. Staff Khan explained control delay. The operational aspect of the delay is not translated into the model. The model could track how long it took a car to go through an intersection and wait at the signal. But the spill over effect would not show up in the urban street LOS. That would be critical for autos and transit. Commissioner Krueger inquired if the model allowed for spillover traffic. He asked if riders may take alternate routes or if the model is preprogrammed to take certain streets. Staff Khan replied that it depends If using imTraffic, a micro-simulation model, the queues are simulated along with the spill over effect and if you have coded all the streets in the area it will show that there is a spillover effect and some traffic may get diverted. It all depends on how much information is put into the model. Staff Bergman finished up with Alternative 2; transit threshold. Stated that the Commission had asked for additional feedback from AC Transit; that was presented. Regarding pedestrian LOS for both modes, the Commission had asked that it be set at B. In Dowling & Associates' analysis, there were ten corridors and 14 intersections; bicycle and transit mode used segment as the unit of analysis; pedestrians and autos looked at intersections and compared the 2007 data to the anticipated 2030 conditions; determined which modes had the most significant impacts; identified some mitigations; looked at the impacts of implementing mitigations on other modes. Question about pedestrian LOS B at intersections was raised at last meeting. This was tested at a few intersections; relatively few intersections in the City where there are significant problems; Dowling tried to achieve LOS B for pedestrians at intersections of Ralph Appezzato Memorial Parkway/Atlantic Avenue with Webster Street and the intersection of Atlantic Avenue at Constitution Way. It was found that LOS B for pedestrians was not feasible at these locations because of the queues being so long that the model could not analyze them. Chair Knox White stated that it was never the Commission' S intention to suggest that locations currently at LOS C or D would be brought up to B. Chair Knox White stated that the Commission had asked for the study to be done with the LOS B. He stated that their intent was to say that if an intersection is already at D, the threshold Page 5 of 15 | TransportationCommission/2009-04-22.pdf |