This Chapter presents general guidance for the preparation of traffic studies that are frequently required in support of requested State highway access and/or local land use and development approvals. Detailed requirements are found in the referenced publications. Please note that a considerable engineering effort may be necessary in the preparation of acceptable traffic studies and mitigation concepts for development projects. Significant highway improvements and traffic control measures may be required to mitigate development impacts. Sufficient time for resolution of complex highway capacity and traffic engineering issues with State and local government should be anticipated and planned into development schedules.
Applicants for access to any State road from a major development and/or a development that may have a significant impact upon the State’s highway system may be required to submit a traffic impact study (TIS) to determine the type of access and scope of required highway improvements required to accommodate the proposed development. A TIS focusing on service conditions at the requested access point(s) and nearby intersections is generally required by SHA for any proposed development that will generate more than 50 peak hour trips, as determined using the Institute of Transportation Engineers' Trip Generation, current edition. The study may be required by SHA in connection with the access permit process and/or by the local jurisdiction in connection with the land use and development approval process.
TIS preparation must conform to all applicable State and local guidelines, using the specified analytical methods. The TIS shall evaluate the impact of total traffic on the State highway intersections and identify appropriate and feasible road improvements to mitigate the impact in accordance with SHA’s guidelines. In addition, mitigation for existing safety or operational deficiencies that would be adversely affected by increased traffic shall be identified. The potential for traffic signal installation or modification must also be addressed as appropriate, as discussed in 6.2.
Applicants should note that complete and accurate documentation of traffic data, field conditions, and assumptions supporting the analysis is necessary to facilitate timely review of the TIS. Specific arrangements for site access must be accurately represented in the study and appropriate evidence must be submitted regarding access arrangements involving adjacent properties, master-planned facilities, and local capital improvement projects. For major developments a preliminary site plan indicating access proposals supported in the TIS should accompany any TIS submitted.
Detailed information and specific requirements regarding TIS preparation are contained in SHA's Guidelines for Traffic Impact Reports/Studies. These guidelines, current at the time of this publication, are included in Appendix E.
When the results of the TIS indicate that a traffic signal or other traffic control device may be necessary, the applicant shall prepare a Traffic Signal Warrant Analysis (TSWA) to accompany the TIS. The TSWA and TIS shall be prepared as two separate documents; however, they may be submitted concurrently for review.
Potential signalization shall be evaluated in accordance with the warrants established in the Manual on Uniform Traffic Control Devices and pertinent SHA guidelines. Applicants should note that traffic signals are not necessarily an appropriate solution for existing or anticipated traffic and safety problems. Operational alternatives to signalization must be thoroughly explored to the satisfaction of SHA in accordance with accepted traffic engineering practices.
While a TIS and/or TSWA may address signalization issues and identify a condition that potentially warrants a signal, the final determination on whether a traffic signal is justified and will be permitted rests with the SHA Office of Traffic and Safety.
Once the need for a traffic impact study has been identified, a study scoping meeting should be arranged with appropriate representatives of the SHA and/or local jurisdiction. The purpose of this meeting is to discuss site specific information concerning the development, confirm the required scope of the study, and discuss anticipated technical issues, assumptions, and concerns. The developer's professional representatives are responsible for initiating this meeting, working through AM and the local jurisdiction.
Traffic Impact Studies shall be submitted to SHA District Office for the county in which your project is located. District Office contact information can be found at the top of our home page. Studies are then distributed within SHA and review comments and input are solicited from the following sources:
AM consolidates the comments obtained from the various review offices, reconciles any differences, and produces a single letter outlining SHA’s comments and requirements with respect to the TIS. The letter either indicates concurrence with the study as submitted or indicates that submission of a revised study is necessary. A complete study, reflecting all revisions, comments, and follow up information, must be submitted before SHA approval will be given.
When an acceptable TIS and TSWA are submitted concurrently, SHA will generate a comment letter that addresses both studies and offers a specific preliminary conceptual approval or denial of the proposed traffic signal. This is only possible if both studies are complete and properly prepared in accordance with SHA guidelines.
Applicants and their professional representatives should contact AM with any questions or concerns during this process. AM will arrange for a meeting, if necessary, with the appropriate SHA staff to review the applicant’s concerns.
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