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Thread: Traffic impact study requirements

  1. #1
    Cyburbian transguy's avatar
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    Traffic impact study requirements

    Anybody know of any good examples of municipal requirements for Traffic Imapact Studies? I'm looking for something that is fairly formal that lays out basic requirements for studies. Thanks for the help!

  2. #2
    Cyburbian Flying Monkeys's avatar
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    Google it you will find tons of them....but it is really specific to your location. For example, in Florida traffic impact studies feed into prop share or impact fee assessment. In other states the goal is to just get an understanding of what will fail.

    You need to think about this carefully and run some scenarios. You will find that your required 'area of influence' will make all the difference. Some places keep it to a mile, some go 5 miles. In Florida we may even carry it out further based on the number of trips over the max service volume of the roadway.

    What state are you in? This would help so that the right persons could give you examples for your area.
    What’s in a name? – Your reputation….:)

  3. #3
    Forums Administrator & Gallery Moderator NHPlanner's avatar
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    Here's our local requirements:

    3.14 TRAFFIC IMPACT ANALYSIS
    a. SUBMITTALS: All projects must provide a report meeting the requirements outlined for a “short” traffic impact analysis. If any of the following conditions apply, then a “full” traffic impact analysis must be completed:
    1. Trip generation exceeding 1,000 average daily trips or 100 peak hour trips. Peak hour is defined as any of the following:
    i. AM peak hour (7-9 AM);
    ii. PM peak hour (4-6 PM);
    iii. Saturday midday peak hour (11AM-1PM); and
    iv. peak hour generator for certain land uses (e.g., school, movie theater) if it falls outside the three previously listed periods. Analysis of Saturday midday peak only applies to retail uses.
    2. The Planning Department may require a “Full” analysis because of special circumstances.

    b. REQUIRED FOR “SHORT” ANALYSES: The “Short” analysis has two primary objectives: First, to justify that a “Full” analysis is not required, and, second, to determine the appropriate impact fee (as outlined in the Zoning Ordinance) imposed on the proponent. At a minimum, the “Short” analysis must include the following:
    1. Description of Site: A brief narrative of the character of the site and adjacent properties, including land uses and other pertinent facts.
    2. Description of Roadways: A brief narrative of the study area roadway facilities, including the number of lanes, speed limit, major intersections, and locations of existing driveways. A description of pedestrian amenities such as sidewalks, crosswalks, and handicap ramps should also be completed.
    3. Sight Distance: Measurements shall be provided for each driveway. A comparison of the available sight distance at each study intersection with Town of X standards shall be included.
    4. Trip Generation: In all cases, the analysis shall include trip generation based upon the ITE Trip Generation Handbook - latest edition. Where the applicant feels the ITE trip generation is not representative of the proposed development, justification must be provided for alternative trip generation methodology. If counts are performed to determine trip generation rates, the applicant must conduct two separate counts and provide full details of the count locations, including the size of the facility, percent occupancy, location, adjacent road Average Daily Traffic (ADT), time, and date of count.
    5. Trip Distribution: At the “Short” analysis level, trip distribution shall be described in a report that demonstrates knowledge of area-wide land uses, roadway facilities, and predominant traffic flows by time of day. The analysis shall contain a percentage distribution of trips (by direction) to the adjacent roadway facilities and any relevant assumptions. All assumptions made shall be outlined, with justification, in the report.
    6. The report shall be stamped by a professional engineer.

    c. REQUIRED FOR “FULL” ANALYSES
    1. The applicant shall meet with the Planning Department to confirm the study area and study area requirements.
    2. General Requirements: All information described in the “Short” analysis must also be contained in the “Full” analysis.
    3. Existing Traffic Counts: In no case shall existing traffic counts used in the analysis be more than two years old (from date of count to date of analysis submittal). If a significant change (e.g., new roadway or development) has occurred within the last two years, the Planning Department and/or Department of Public Works can, at their discretion, require that new counts be conducted. Traffic counts shall include information on date, time, day of week, and name of the firm or individual who performed the counts. Traffic counts shall be seasonally adjusted to average and peak conditions.
    4. Design Year Traffic Projection:
    i. Design Year: The design year for traffic projections shall be 10 years from the current year.
    ii. The applicant shall obtain a list from the Town of Londonderry containing all proposed developments permitted to date within the study area. The traffic generated by these projects shall be added to the no-build and build analyses. Additionally, the background growth rate should be determined based upon information obtained from the NH Department of Transportation or the Southern New Hampshire Regional Planning Commission. The calculated background growth rate should be completely documented and included in the study for review.
    iii. Trip Generation: Traffic projection for trip generation growth is described in the “Short” analysis section.
    iv. Trip Distribution: The applicant shall provide justification for the assumed trip distribution. The trip distribution methodology should be representative of the type of development. Data may be obtained from employee zip code analysis, studies of similar sites, analysis of ADT on adjacent roadways, US Census journey to work and home-based work/non-work trips, or other sources. Graphic presentation shall be provided showing 1) peak hour trips added by the development, and 2) study area peak hour traffic volumes under each of the following scenarios:
    a. Existing conditions;
    b. Existing conditions with proposed development;
    c. No build for design year, and;
    d. Build for design year .
    5. Peak Hour Capacity Analysis: Capacity analysis is to be performed at all study intersections (including driveways) using the most current Highway Capacity Manual Level of Service methodology for signalized and unsignalized intersections. Each of the four scenarios listed above must be analyzed at a minimum. A gap acceptance analysis should be provided in the case of adjustment to the default critical gap in the capacity analysis.
    6. Safety Analysis: Accident data for the roadways and intersections included in the study area shall be obtained from the Londonderry Police Department. Accident history for the three most recent years available shall be summarized and compared to the Statewide or national rates established for the corresponding facility type (e.g., rural two-lane highway, urban arterial, etc.).
    i. The minimum all season sight distance shall be three-hundred sixty-five (365) feet in all directions meeting the requirements for roadway intersections and Exhibit D3 of the X Subdivision Regulations.
    7. Trucks: The location of loading docks and/or delivery drop-off areas shall be given in the analysis. The estimated frequency of trucks by time of day shall be provided when the number of daily truck trips exceeds 30 percent of the ADT on any roadway in the study area.
    8. Parking: There should be a defined correlation between estimated trip generation and parking space requirements. The proposal shall contain a comparison of daily and peak hour trip generation estimates to the number of proposed parking spaces on site.
    9. Narrative: Discussion of the following shall be provided:
    i. Travel safety characteristics of any streets substantially impacted by allowing the “build” alternative, considering such things as sight distance limitations, width limitations, horizontal or vertical alignment deficiencies, and surface conditions;
    ii. Streetside safety of any streets substantially impacted, considering such things as the amount and type of development along such streets, presence of sidewalks, vehicle speeds, and any outstanding limitations in sight distance or road configuration;
    iii. Impact on pedestrian safety and convenience;
    iv. Noise impacts on residential premises.
    10. Mitigation: Any mitigating measures proposed shall be described in detail and included in the analysis. It is imperative that the applicants identify improvements to intersections even if they don’t fund them fully. Transportation Demand Management (TDM), non-vehicular transportation and mass transit should be strongly considered as mitigating strategies.

    d. STANDARDS
    1. If not more severely limited under other provisions of other laws or regulations, the absolute increase in calculated intersection delay, under “build” conditions, shall be no more than 10-20 seconds.
    2. Average daily traffic volumes shall not be increased by more than one-third above the “no-build” level on any street.

    e. PROCEDURE
    1. Applicants shall contact the Planning Department early in the project design regarding the scoping of any traffic studies, including consideration of the study area boundary, the definition of “alternative” where involved, and the type of mitigation, if any, which are likely to prove appropriate.
    2. Impact studies shall be submitted at the time of application for site plan review, to allow review prior to the public hearing or meeting at which the project will be presented to the Planning Board.
    "Growth is inevitable and desirable, but destruction of community character is not. The question is not whether your part of the world is going to change. The question is how." -- Edward T. McMahon, The Conservation Fund

  4. #4
    Cyburbian transguy's avatar
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    I work in Missouri. The trouble I am having is that a large portion of anything transporation related is done through the state or county. However, we (a municipality) often require a TIS while rezoning. Previously, someone looked at the study and who prepared it and that was about it. I am trying to make a push to come up with a formal process for when a TIS is required and what information is required (e.g. over 10 acres needs x, y, z). I am trying to find some examples of other municipalities, mainly suburban locations, that have well established requirements that are clear and concise. I don't want anything that seems overbearing to try and minimize outcry from developers.

    Thanks for the comments thus far.

  5. #5
    Cyburbian
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    Here's a link to ours. Admittedly, there's still some fine-tuning they could use, but overall, they're a reasonable start.

    http://www.nashville.gov/mpc/pdfs/ma...l_20040706.pdf

  6. #6
    Cyburbian Flying Monkeys's avatar
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    Quote Originally posted by Tall Fella' View post
    Here's a link to ours. Admittedly, there's still some fine-tuning they could use, but overall, they're a reasonable start.

    http://www.nashville.gov/mpc/pdfs/ma...l_20040706.pdf
    It is a good example Tall Fella....page 6 states that the study area goes to the first collector or major road, but leaves room for the 'Metro Transportation Manager' to add more if deemed important. This gives it some flexibility. I noticed you guys reference the Florida Site Impact Handbook on page 5....you may want to add the version as that manual is currently being updated and may not be as stringent due to the mess Florida has gotten itself into.
    What’s in a name? – Your reputation….:)

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