940.1 Analysis of Retrofit and Permit Applications
Where access is being managed on an existing roadway (a retrofit or permit project), it is often not possible to incorporate all of the access management criteria due to economic, physical or other constraints. Care must be taken to balance economic interests with transportation needs. Economic impacts to business must be carefully considered and efforts must be made to mitigate those impacts. Collaboration with property owners and other stakeholders is the most effective method to achieve improvements that satisfy both operational and economic needs.
The collaboration process begins in the early stages of the project. MoDOT staff is to discuss the fundamentals and benefits of managed access with the stakeholders. Emphasis is to be placed on safety and operational benefits and how those benefits can have a positive impact on property values and the business climate. Most stakeholders are more receptive after they gain an understanding of the concepts.
Understanding the concepts may not completely alleviate concerns. Adjoining property owners can remain hesitant to apply the principles on their properties. Personal meetings with each property owner to discuss and mitigate the needs of their site are often the best way to alleviate the concerns. Multiple meetings with some individuals may be necessary to discuss proposals and their impacts. The resulting design may not be entirely satisfactory to either party. Instead, the goal of the process is to produce acceptable operational and safety impacts while gaining consent of the stakeholders.
In cases where the access management criteria cannot be met, a detailed analysis is to be performed to determine the optimum solution. This solution is to improve safety and operations along the roadway and maintain uninterrupted flow on the transportation system and adequate access to the adjoining properties. Flexibility, good judgment, negotiation and compromise will be necessary to determine the right solution for each location.
While Highway Capacity Manual procedures can quickly predict whether or not a facility will be operating at or below capacity, they are generally limited in their ability to evaluate systems effects, queues and the effects of queues and over-saturated conditions. Additionally, there are several gaps in the Highway Capacity Manual procedures, such as roadways with the following:
- closely spaced traffic signals
- freeway weaves
- other unique scenarios
Where Highway Capacity Manual procedures do not adequately analyze the roadway improvements, a microsimulation analysis may be appropriate. The VISSIM software package is capable to analyze the limitations and gaps of the Highway Capacity Manual. The Highway Capacity Manual may be used as a primary check of a roundabout’s capacity, but additional operational analyses are to use either the SIDRA or VISSIM software package.