1. Roundabouts What is a roundabout?
What is a regular traffic light intersection?
How are they similar and different?
Do you know where any roundabouts are in Lincoln?
What purpose do you think a roundabout serves?
What safety features might a roundabout have verse a regular traffic signal intersection?

2. Roundabout at Sheridan Blvd and S 33rd St., Lincoln, NE

3. Point of Contact
A point of contact is when two or more vehicles collide.
traffic accidents

4. Activity I
With your group you are going to build a regular 4 way intersection.
Supplies:
14 pipe cleaners
4-5 match box cars, trucks, etc.

6. What to do:
Using your pipe cleaners, build a replica of a regular intersection
Once you have your intersection built, simulate different kinds of point of contacts
Record the “different” point of contacts on a piece of paper (you can draw pictures)

7. Roundabouts in action Activity II: Seeing a roundabout in action.
Show the video: working roundabout

8. Make a Roundabout
Now take 2 more pipe cleaners and make a circle that will fit in the middle of your intersection.
Now record the different kinds of point of contacts.
Now lets compare the two different intersections

9. Let’s look at the parts of a roundabout
_____________
Departure Width
Circular Roadway
Width
____________
_____________
Truck Apron
Raised Central
Island
____________
Entry Radius
_____________
____________
Exit Width
_____________
Entry Width
Inscribed Circle
Diameter
_____________
_____________
Central Island
Diameter
_____________
Exit Radius
_____________
Yield Line
_____________
Splitter Island
_____________
Approach Width

10. What parts of a Circle do you know?

11. What parts of a circle do you see? roundabout

12. Problem Solving
 You are designing a roundabout to be built in your neighborhood.
1. The dimensions of the Central Island has a radius of 35’.
What is the diameter?
What is the circumference?

13. What would the diameter of the inscribed circle be?
2. The circulating roadway, that portion of the roundabout between the central island and the inscribed circle is the portion of the roadway used by vehicular traffic. The inscribed circle of the roundabout encloses the circulating roadway. The circulating roadway is approximately 15’ wide.
What would the diameter of the inscribed circle be?
What would the circumference be?

14. Stopping Sight Distance
Stopping Sight Distance (SSD) is the distance between the hazard and the approaching driver, measured along the vehicle path. It is used to assess safety for vehicle to vehicle and vehicle to pedestrian or bicycle hazards.
When a vehicle is approaching a roundabout, it needs to have time to see and react safely to enter the roundabout.

15. Converting mph to ft/sec
Let’s look at the equation below

16. Distance traveled during braking:
V = initial vehicle speed in ft/sec
a = 11.2 ft/s

17. Distance traveled during perception-reaction time is:
V = initial vehicle speed in ft/sec
t = 2.5 sec

18. Stopping Sight Distance
Now combine the two

19. Now let’s look at a current project at 14th & Superior
Show the video: