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A Handbook That Outlines When traffic impact studies should be required What analyses should be included How the study should be reviewed and used Who.

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Presentation on theme: "A Handbook That Outlines When traffic impact studies should be required What analyses should be included How the study should be reviewed and used Who."— Presentation transcript:


2 A Handbook That Outlines When traffic impact studies should be required What analyses should be included How the study should be reviewed and used Who is qualified to prepare and review impact studies



5 Current Problems Communities do not adequately address traffic implications of zoning and land use decisions. A standard practice is needed. Site traffic impacts are often ignored, misunderstood or inappropriately used. Mitigation measures are not addressed.




9 What Can Traffic Impact Studies Do? Forecast traffic impacts. Assist in evaluation of rezonings and proposed land developments. Evaluate number/location of access points. Identify a basis to allocate costs of improvements. Help promote a coordinated review.

10 Elements of Handbook Why is a Traffic Study Needed? When is a Study Needed and What Type is Required? Impact Analyses Site Access and Circulation Review Mitigation Analysis Qualifications of Preparer and Reviewer Review Process and Coordination

11 Preliminary Considerations When traffic studies should be required. Require different types of traffic impact studies based on scale of development. Pre-application conference to discuss specific issues.

12 Types of Traffic Studies Rezonings: contrasting impacts of representative uses for current v. requested zoning. Traffic Impact Assessment: smaller projects, analyze site access points. Traffic Impact Statement: traditional traffic study, includes nearby signalized intersections. Regional Traffic Analysis: comprehensive study of a large area.



15 Trip Generation Sources Trip Generation, a nationally recognized manual published by the Institute of Transportation Engineers (ITE). Recent local data from at least three similar uses.


17 When Should Traffic Impact Studies be Required for Rezonings? Rezoning inconsistent with Master Plan if potential uses could generate 100+ more peak hour directional trips than uses under current zoning. Rezoning consistent with Master Plan but generate 1,000 daily trips or rezoning is considered premature because of traffic conditions. Rezoning along designated “congested,” “critical” or “safety management” corridors. Rezoning studies evaluate representative or worst case uses, not just a particular use.

18 When Should Traffic Impact Studies Be Required? Projects Which…Type of Study Required…. Generate > or 500 or < 750 trips daily Impact Statement Generate 100-500 pk. hr. dir. trips or 750 + trips daily Impact Statement Are along identified corridorsVaries Involve “significant” change or expansion to PUD or use Varies Generate 500+ dir. pk. hr. Regional Analysis Other cases – Special Land Uses, etc. Varies

19 Peak Hours Traffic impacts should be evaluated for a typical week day : a.m. peak hour of adjacent streets p.m. peak hour of adjacent streets Saturday peak hour for certain commercial uses daily traffic figures useful for planning

20 Examples of Trip Generation to Meet Study Thresholds Use 50 Peak Hr. Dir. 100 Peak Hr. Dir. Single Family Units70150 Apartment units115245 Shopping Centers (sq. ft.) 5,20015,500 Fast Food Restaurant (sq. ft.) 2,6005,200 Office (sq. ft.)22,00055,000 Light Industrial (sq. ft.)58,000115,000


22 Rezoning Traffic Study- Compare Uses Current Office Zoning – Municipal Offices – General Offices – Medical Offices – Funeral Homes Proposed Commercial Zoning – Offices – General Retail – Gas Stations – Restaurants – Motels – Shopping Centers





27 Preapplication Conference Who to involve…. Items to discuss  type of study needed  study area  availability of data  background traffic growth  other nearby projects to include  programmed roadway improvements  trip generation sources/trip reduction factors  horizon year  other issues


29 Traffic Impact Study Should Include 1.Recent traffic counts, especially peak hour(s) 2.Existing levels of service analysis 3.Background traffic growth 4.Trip generation of project 5.Trip distribution rationale

30 Traffic Impact Study Should Include 6.Future levels of service 7.Crash (accident) history, if appropriate 8.Site access and internal site circulation review 9.Mitigation alternatives and recommendations





35 Levels of Service (LoS) Analysis LoS mathematically measures traffic operations. Based on vehicle delays for various movements. Best measured for peak hours. Scale A-F A/B = no or little delay C/D = some delays, typical design standard E = volumes near or at capacity, congestion F = significant congestion/delays

36 Examples LoS Summary Signalized Intersection Approach A.M. Peak Hour Delay (sec.) LoS P.M. Peak Hour Delay (sec.) LoS Eastbound 34.1 D 46.9 E Westbound 26.7 D 41.1 A Northbound 18.2 C 17.7 C Southbound 124.1 F 20.9 C Overall 52.9 E 32.1 D





41 Evaluation of Mitigation Alternatives Roadway improvements – bypass lane, deceleration lane, widening, construct new street, etc. Access management techniques – service drives, deceleration lanes, prohibit certain turns, median, etc. Operational improvements – install traffic signal(s) or change timing, demand management techniques, uses of public transit, etc. Responsibility, timing and funding.








49 Implementation Master planning and corridor planning Adopt or amend ordinances Staff training Agency coordination

50 Revise Ordinances Incorporate model ordinance as a General Provision Reference in the site plan review section List uses meeting the thresholds as special land uses Encourage mixed use developments and connections between developments Adopt access management standards Require submittal of a study for certain rezonings through “Ordinance Amendment” regulations

51 Qualifications 3+ years recent experience preparing traffic impact studies Impact studies comprise a major component of preparer’s work Familiarity with the Highway Capacity Manual Education or training in traffic impact analyses Member of ITE or TRB Registered PE/AICP/PCP or professional transportation planner Any signal or design work should be prepared by a PE trained in traffic engineering.

52 Summary of Michigan Cases and Constitutional Issues: Subdivision Control Act, Mobile Home Act and Zoning Enabling acts do not authorize requiring a developer to fund off-site improvements. Constitutionality of off-site improvements has been upheld under the driveway permit approval process.

53 Traffic Study Review: Training/Coordination Training staff and/or use consultants. Obtain reference materials. Establish a review system between the community and local road agency and/or MDOT. Coordinate with MPO, 3-C, Public Transit or Regional Planning Agencies.


55 Other Important Tools to Manage Traffic: State/MPO long range plans Master plans Corridor plans Thoroughfare plans Access management Right-of-way preservation Zoning/subdivision regulations Mixed use developments Public Transit Transportation demand management


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