15.A.
City Council Meeting - FINAL
- Meeting Date:
- 05/01/2018
- From:
- Jeff Bauman, Traffic Engineer
Information
TITLE
Discussion: Review of the Traffic Impact Policy that allows the traffic rating of a road to degrade as a result of development
STAFF RECOMMENDED ACTION:
Council direction.
EXECUTIVE SUMMARY:
Councilmember Putzova provided a Future Agenda Item Request on September 19, 2017, for Review of the Traffic Impact Policy that allows the traffic rating of a road to degrade as a result of development. In an effort to populate this discussion item with background information relating to the City's current practices regarding Transportation Impact Analyses and specifically Level of Service thresholds, the staff has prepared the following informational summary.
INFORMATION:
The City currently utilizes a nationally accepted Transportation Impact Analysis (TIA) process based upon the Institute of Transportation Engineers and the Arizona Department of Transportation’s TIA for Development Guidelines. While each jurisdiction may customize the analysis--such as using local trip generation data for some land uses (as Flagstaff does for student housing) or using different criteria for what impacts are acceptable--the basic steps are the same for a TIA. In Flagstaff, the review process is highlighted by these two fundamental points: (1) a TIA is generally required of all projects that generate a minimum of 100 Peak Hour trips, and (2) it allows a roadway element LOS to degrade as a result of a project from current operations LOS (A, B, or C) to LOS D without requiring mitigation. Developments that push a transportation element past LOS D must mitigate their transportation impacts back to LOS D or better.
LOS D is the most widely used threshold for transportation facility operations before mitigation is required, as it is the point where the facility is nearing capacity but not so close to capacity that the facility becomes unstable. When a facility operates right at capacity (LOS D to E threshold), a small disturbance can result in an almost instantaneous reduction in LOS and unstable flow. While vehicles absorbed into a transportation system at LOS A, B, or C do increase delay, the increased delay is not perceived as significant or as causing a facility failure. On the other hand, absorbing vehicles into a system that is already operating near the lower limit of LOS D, E, or F category can have a significant and sometimes dramatic impact on facility operations and delay.
One option that has been discussed is requiring new development to mitigate back to the LOS that was in place before the development added trips to the system. However, this approach has its own shortcomings and is not widely, if at all, accepted in the industry. When a roadway is operating at LOS A it has very few trips and operates in a free flow condition at all times of the day. If a development were proposed to add trips to this roadway, the LOS may be anticipated to move to LOS B, which would still be almost free flow. To most, the difference between LOS A and B would be unnoticeable. To mitigate back to LOS A, the roadway would likely need to be widened, which would be a disproportionately costly improvement to mitigate a slight increase in traffic. Requiring this level of mitigation would be unnecessary because the road would function adequately at LOS B, wasteful for the municipality to maintain, require increased ROW widths impacting adjacent business’ and homes, and result in mitigation for most projects of any significant size.
The Institute of Transportation Engineers (ITE) is beginning a process to update its Transportation Impact Analysis for Site Development guidelines which are the foundational document for many agencies TIA procedures, including the City of Flagstaff. The new document will be called the Multimodal Transportation Impact Analysis for Site Development. The updates will focus on emerging trends in transportation including multimodal measures of effectiveness, free-rider and last-in concepts, infill development impact analysis, context-sensitive solutions and emerging technologies. The updated ITE guidelines potentially address many of the concerns that staff has heard from the community and the City Council regarding the current City TIA process. With this in mind, the City nominated a Transportation Engineering PM (Alan Sanderson) to be a part of the national steering committee charged with drafting the updates. Alan was accepted as a member of the committee, and has been attending conference calls and will attend the committee meetings during this summer’s International ITE meeting. Staff is excited to be a part of this project and anticipates relying heavily on the new recommended practice as we update the City’s TIA process in the next 12 – 18 months.
LOS D is the most widely used threshold for transportation facility operations before mitigation is required, as it is the point where the facility is nearing capacity but not so close to capacity that the facility becomes unstable. When a facility operates right at capacity (LOS D to E threshold), a small disturbance can result in an almost instantaneous reduction in LOS and unstable flow. While vehicles absorbed into a transportation system at LOS A, B, or C do increase delay, the increased delay is not perceived as significant or as causing a facility failure. On the other hand, absorbing vehicles into a system that is already operating near the lower limit of LOS D, E, or F category can have a significant and sometimes dramatic impact on facility operations and delay.
One option that has been discussed is requiring new development to mitigate back to the LOS that was in place before the development added trips to the system. However, this approach has its own shortcomings and is not widely, if at all, accepted in the industry. When a roadway is operating at LOS A it has very few trips and operates in a free flow condition at all times of the day. If a development were proposed to add trips to this roadway, the LOS may be anticipated to move to LOS B, which would still be almost free flow. To most, the difference between LOS A and B would be unnoticeable. To mitigate back to LOS A, the roadway would likely need to be widened, which would be a disproportionately costly improvement to mitigate a slight increase in traffic. Requiring this level of mitigation would be unnecessary because the road would function adequately at LOS B, wasteful for the municipality to maintain, require increased ROW widths impacting adjacent business’ and homes, and result in mitigation for most projects of any significant size.
The Institute of Transportation Engineers (ITE) is beginning a process to update its Transportation Impact Analysis for Site Development guidelines which are the foundational document for many agencies TIA procedures, including the City of Flagstaff. The new document will be called the Multimodal Transportation Impact Analysis for Site Development. The updates will focus on emerging trends in transportation including multimodal measures of effectiveness, free-rider and last-in concepts, infill development impact analysis, context-sensitive solutions and emerging technologies. The updated ITE guidelines potentially address many of the concerns that staff has heard from the community and the City Council regarding the current City TIA process. With this in mind, the City nominated a Transportation Engineering PM (Alan Sanderson) to be a part of the national steering committee charged with drafting the updates. Alan was accepted as a member of the committee, and has been attending conference calls and will attend the committee meetings during this summer’s International ITE meeting. Staff is excited to be a part of this project and anticipates relying heavily on the new recommended practice as we update the City’s TIA process in the next 12 – 18 months.