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Thread: Community guidelines for traffic impact studies?

  1. #1

    Community guidelines for traffic impact studies?

    Hey all,

    I am going to be starting work soon on a guidebook for our local communities that will, among other things, attempt to assist them with understanding when traffic impact studies should be done, as well as what should be included in them, how to review them, etc....

    I was wondering if any of you know of communities or regions that have regulations or guidelines for dealing with traffic impact studies that I might use as examples or at least as part of the research for this thing.

    Thanks for any input.

    MW

  2. #2
    Forums Administrator & Gallery Moderator NHPlanner's avatar
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    Here's what we use in Londonderry (from our Site Plan Regulations):

    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 Section XXII of 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 Londonderry 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 Londonderry 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

  3. #3
    maudit anglais
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    PM me with your email and I can send you a copy of the City of Toronto's Guidelines.

  4. #4
    Thanks, I appreciate the help.

  5. #5
    Cyburbian The One's avatar
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    Hmmm....

    While the 1,000 trips number is an ok starting point for requiring TIA's, don't be shy about asking for a two or three page letter from a Traffic Planner/Engineer that outlines the key stats for smaller sites. These can really help keep you out of trouble later on or at the very least help identify negative trends or problems.....

    I tend to think that in a smaller city or county you should be able to justify requiring a TIA at 500 trips+. Since the traffic impacts tend to be more pronounced in smaller jurisdictions, it makes sense that you would want to better understand all of the implications involved......just my two-cents
    Skilled Adoxographer

  6. #6
    Forums Administrator & Gallery Moderator NHPlanner's avatar
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    Quote Originally posted by The One
    While the 1,000 trips number is an ok starting point for requiring TIA's, don't be shy about asking for a two or three page letter from a Traffic Planner/Engineer that outlines the key stats for smaller sites. These can really help keep you out of trouble later on or at the very least help identify negative trends or problems.....

    I tend to think that in a smaller city or county you should be able to justify requiring a TIA at 500 trips+. Since the traffic impacts tend to be more pronounced in smaller jurisdictions, it makes sense that you would want to better understand all of the implications involved......just my two-cents
    If you read it carefully, we require a TIA for ALL projects....the 1000 trip level just kicks it from a "short analysis" to a "full analysis."
    "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

  7. #7
    Cyburbian The One's avatar
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    Oh yeah.....

    Quote Originally posted by NHPlanner
    If you read it carefully, we require a TIA for ALL projects....the 1000 trip level just kicks it from a "short analysis" to a "full analysis."
    Yes, but a full blown TIA for 10 new homes is silly.....and could be covered by a simple 2 page letter from the traffic engineer..... remember, all those fees get tacked on to the already over priced homes being built.....
    Skilled Adoxographer

  8. #8
    Forums Administrator & Gallery Moderator NHPlanner's avatar
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    Quote Originally posted by The One
    Yes, but a full blown TIA for 10 new homes is silly.....and could be covered by a simple 2 page letter from the traffic engineer..... remember, all those fees get tacked on to the already over priced homes being built.....
    Maybe it's a regional terminology thing.....but we require TIA's for site plans (commercial, industrial, multi-family developments). Our subdivision regulations do not have TIA requirements, but we do typically ask for the "short anaylsis" for most subdivisions as well. A short analysis is typically 2-3 pages long using ITE and a rough distribution of the trips.....not an onerous requirement from my perspective.
    "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

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