At – Grade Intersections
Signalization entails significant costs and ongoing maintenance and should be implemented only when necessary. Signalization is discouraged when safety and operational concerns at uncontrolled intersections may be addressed by other treatments such as implementing a yield or stop condition, signing, roadway lighting, or minor geometric changes. Signal warrants should be met before considering a traffic signal as a viable option; however, meeting signal warrants does not mean that a signal should be installed. A traffic study needs to be completed to evaluate each alternative to determine which one would provide the most benefit. In some cases, even if a signal is warranted, other treatments such as roundabouts or no-build may provide the greatest benefit/cost.
Existing traffic signals should be evaluated to see if timing can be optimized for specific locations, or if within a corridor, multiple signals may need to be coordinated in order to improve performance. Network solutions or innovative at-grade intersection designs should be considered when appropriate to help reduce the cost of traditional geometric and operational solutions. Some examples of innovative intersection designs may include Continuous Flow Intersections, Michigan U-Turns, J-Turns, Maryland T’s, etc. Impacts to all roadway users who will use the facilities should be considered.
Grade – Separated Interchanges
Grade separation should be selected when conflicting high traffic volumes exceed those that can be handled efficiently and safely with an at-grade intersection. Occasionally, it may be appropriate to grade separate an intersection with a disproportionate rate of crashes that is not likely to be reduced through at-grade improvements or an intersection on a corridor transitioning to full access control. Impacts to all roadway users who will use the facilities should be considered.
Consider options to maintain elements of the existing interchange and replace only those elements needing improvement before considering full reconstruction options. Innovative solutions such as a Diverging Diamond Interchange or ramp metering can be considered to address needs while minimizing impacts and costs.
New interchanges should be appropriately spaced to eliminate conflict with existing interchanges within the corridor.