40.4.3. Entry, exit and island radius

Try these first

1. 1.

   What is the purpose of the entry radius in a rotary?

   Hint

   Think about how curves influence driving speed.

2. 2.

   Why should the exit radius be larger than the entry radius?

   Hint

   Consider traffic flow efficiency.

3. 3.

   What should be the ideal speed for vehicles at the entry of an urban rotary?

   • 30 km/h
   • 20 km/h
   • 25 km/h

   Hint

   Reflect on speed limits discussed in the section.

4. 4.

   True or False: The exit radius should generally be less than the entry radius.

   • True
   • False

   Hint

   Think about traffic flow dynamics.

5. 5.

   Design a rotary for a suburban area where the approaching traffic volume is moderate. Discuss how you would determine the entry and exit radii based on expected speed limits and pedestrian traffic.

   Hint

   Consider ratios and pedestrian flow discussed in the text.

6. 6.

   Analyze the relationship between the entry and exit radii in a busy urban rotary and propose measurements based on the design requirements of reducing speed and accommodating heavy traffic.

   Hint

   Look at the problem from both a safety and flow perspective.