Unsignalized Intersections

Abstract

Unsignalized intersections are those where at least one of the movements is controlled by a STOP or a YIELD sign. Operations of such facilities require the drivers on the controlled movements (usually referred to as minor movements) to judge the size of the gaps along the major (or uncontrolled) street and select a suitable one to cross, or to merge into.

Problems

• 1. Conduct a literature review to document the methods for obtaining the critical gap of unsignalized intersection approaches. Which one would you recommend?

• 2. Examine your favorite microsimulator and document its algorithms for analyzing roundabouts. How does the model handle the differences between a STOP sign and a YIELD sign used at TWSC intersections? How does the model handle critical gap determination for various driver populations and various vehicle types?

• 3. For the intersection of Example 11.2, use the HCM7 to calculate the capacity of the NB left-turn movement if it is provided its own lane and the demand of the WB through movement is 670 vph. How does the capacity of this movement change if the NB approach has a single lane? Assume that the demand of the NB left is 150 vph.

• 4. Conduct a literature review to identify the methods for the analysis of AWSC intersections. Document the process for estimating the probability of the presence of vehicles in the opposing and conflicting approaches.

• 5. Consider the demands shown in the figure below. Use your favorite microsimulator to evaluate the performance of an intersection if it is assumed that it is a TWSC, an AWSC or a roundabout intersection. Which of the three designs is most effective for this particular set of demands? How would your response change as a function of the relative demands?

  

• 6. Conduct a literature review to identify the guidelines when roundabouts are operationally more effective than TWSC or AWSC intersections.