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Transportation Impact Analysis Presented By Katy Flynn, P.E. Fehr & Peers February 19, 2008.

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Presentation on theme: "Transportation Impact Analysis Presented By Katy Flynn, P.E. Fehr & Peers February 19, 2008."— Presentation transcript:

1 Transportation Impact Analysis Presented By Katy Flynn, P.E. Fehr & Peers February 19, 2008

2 Presentation Overview What is a Transportation Impact Analysis? Why do we prepare Transportation Impact Analyses? How do we prepare a Transportation Impact Analysis?

3 What is a Transportation Impact Analysis (TIA)? A Transportation Impact Analysis evaluates the impacts of a proposed project on the surrounding transportation system and identifies measures to mitigate significant impacts.

4 Why Do We Prepare TIAs? Evaluate Project Impacts Agency Requirements Criteria – Project meets a trip threshold (for Washoe County the Threshold is 80 or more trips during the peak hour or 750 or more on a daily basis), controversial project, nearby intersections that operate at a poor level of service, safety issues Evaluate Land Use/Development Options Environmental Laws NEPA (National Environmental Policy Act) CEQA (California Environmental Quality Act) Assess Impact Fees

5 How do we prepare a TIA? – Getting Started Determining if a TIA is required? Obtain Site Plan (Get involved in site plan development) Evaluate Criteria Scoping Process Talk to jurisdiction/agency staff Determine: Study Area Analysis Time Periods (AM Peak, PM Peak, etc.) Analysis Scenarios (Existing, Background, Project, Cumulative, Phasing, Alternatives) LOS Calculation Methods (2000 HCM, Circular 212) Significance Criteria (LOS Thresholds, Left-turn Queues, Neighborhood Issues, Neighborhood Intrusion, Safety Issues)

6 How do we prepare a TIA? – Site Reconnaissance & Data Collection Visit the Site to Collect: Lane configurations Traffic control devices Speed limits Turn lane lengths Transit stops Pedestrian facilities Observe study period conditions Data collection: Turning movement intersection counts ADT Vehicle classification Accident history

7 How do we prepare a TIA? – Analysis Determine the appropriate tool for the analysis: Isolated intersection analysis vs. micro-simulation

8 How do we prepare a TIA? – Project Trip Generation Published Rates (ITE, RTC, Caltrans), surveys Factors that affect vehicle trip generation: Pass-By trips, Internalization, transit, and others

9 How do we prepare a TIA? – Project Trip Distribution Existing Travel Patterns Complementary Land Uses (i.e. Residential and Office Uses) Zip Code Data Census Data Travel Demand Model Engineering Judgment

10 How do we prepare a TIA? – Project Conditions Analysis Add project traffic to existing conditions Analyze LOS, Queuing, Impacts to transit/pedestrian facilities/bicycle facilities, etc. Determine Impacts Recommend mitigation measures…

11 How do we prepare a TIA? – Project Conditions Analysis – Mitigation Measures Traffic Signals Signal Warrants Lane Additions Access Modifications/ Access Management Changes to Project Description Left-Turn Restrictions Roundabouts Roadway Widening Traffic Signal Coordination Transportation Demand Management Programs Impact Fees

12 How do we prepare a TIA? – Cumulative Conditions/Future Year Analysis 20 to 30 year horizon Typically a planning level analysis – roadway segment Determine future traffic volumes Travel Demand Model Growth Rate Historical Data Known long term projects General Plan documents

13 How do we prepare a TIA? – Site Access Private Driveway Design Criteria Location/Spacing Permitted Turning Movements Signalization Width Offsets Grade Emergency Vehicle Access Sight Distance

14 How do we prepare a TIA? – Site Circulation Throat Depth Requirements Source: Access Management Manual (TRB) Source: Transportation and Land Development (ITE) Driveway Width Source: NDOT Access Management System and Standards, 1999

15 How do we prepare a TIA? – Site Circulation Drive Aisle Width Dead-End Drive Aisles Pedestrian Conflicts Parking Supply vs. Demand Truck Delivery Movements

16 How do we prepare a TIA? – Site Circulation

17 Reno, NV Denver, CO Salt Lake City, UT San Francisco, CA Walnut Creek, CA Roseville, CA Sacramento, CA San Jose, CA Los Angeles County, CA Orange County, CA


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