1. Road Diets and Roundabouts
Paul Zykofsky, AICP
Local Government Commission
Sacramento, CA

2. “Classic Road Diet” 4 to 3 lanes San Antonio TX
In most people’s minds, this is what is understood by the term road diet. We’ll discuss it, but show some other options.
4 to 3 lanes
San Antonio TX 2

3. Road diets: reclaim street space for other uses
Bike Lanes
Median
On-street parking
A road diet typically reduces the number of travel lanes on a road, and dedicates the space to other uses. Road diets usually result in enough room to provide bike lanes, but that’s not the only benefit.
Center Turn-Lane
Road diets: reclaim street space for other uses
Seattle WA 3

4. 3 crash types can be reduced by going from 4 to 3 lanes: 1 – rear endersX
Road Diets and Traffic Operations 4 4

5. 3 crash types can be reduced by going from 4 to 3 lanes: 2 – side swipesX
Road Diets and Traffic Operations 5 5

6. 3 crash types can be reduced by going from 4 to 3 lanes: 3 – left turn/broadsideX
Road Diets and Traffic Operations 6 6

7. Road Diets in Seattle (4 to 3 lanes)

8. Benefits of road diets for bicyclists and pedestrians?
Provide space to add bicycle lanes
Reduce crossing distance
Eliminate or reduce “multiple threat” crash types
Install crossing island to cross in 2 simple steps
Reduce top end travel speeds
Buffer sidewalk from travel lanes (parking or bike lane)
Reclaim street space for “higher and better use” than moving peak hour traffic
Animated – let participants give some answers before clicking. They probably won’t get all of them, that’s okay. 8

9. Before
Charlotte NC

10. After
Before
Reclaiming road space creates room for bicycle lanes and pedestrian islands
Charlotte NC

11. Case study: Edgewater Drive Resurfacing Project (Orlando, FL)
$589,000 project scheduled in FDOT 5-year work plan
FDOT open to 3-lane option if City takes over jurisdiction
Changes must be accepted by neighborhood and business associations; before/after studies
Before
Concept

12. Reality: Before

13. Reality: After

14. Before/after studies: 1. Crash rate
34% Reduction
1 crash every 2.5 days
1 crash every 4.2 days
(146 per yr)
(87 per yr)

15. Before/after studies: 2. Injury rate
68% Reduction
1 injury every 9 days
(41 per yr)
1 injury every 30 days
(12 per yr)

16. Before/after studies: 3. Speeding analysis

17. Before/after studies: 4. Traffic volumes
Now
21,000+

18. Before/after studies:
5. On-street parking utilization

19. Before/after studies: 6. Pedestrian volumes
23% Increase

20. Before/after studies: 7. Bicyclist volumes
30% Increase

21. Road Diet — Before Pottstown, PA
There are many possibilities; a typical 5-lane can be converted to (next slide)
Road Diet — Before Pottstown, PA

22. Road Diet — After Pottstown, PA
3-lanes with bike lanes. Note on one side parallel parking was changed to back-in diagonal parking, much better for cyclists and drivers.
Road Diet — After Pottstown, PA

23. There’s potential on one-way streets too:
One-way streets have high potential, as they tend to be overbuilt. In this example, most of the street is underutilized. This photo was taken off-peak, but it is the way the street looks most of the day.
There’s potential on one-way streets too:
Is this street operating at capacity?
Boise ID 23

24. One-way streets have high potential, as they tend to be overbuilt
One-way streets have high potential, as they tend to be overbuilt. Many 4-lane two-way streets were converted to 4-lane one-way streets with no analysis. In many cases, 3 lanes in one direction carries traffic just as well. In this example, the street life came about after the roadway was narrowed form 4 to 3 lanes, crating space for bike lanes and wider sidewalks.
Road Diet on one-way street: This area was recaptured from a 4th travel lane; the street took on a whole new life
Portland OR 24

25. 68 Feet
La Jolla Boulevard, Bird Rock, San Diego, California Before

26. La Jolla Boulevard, Bird Rock, San Diego, California After
14 Feet
La Jolla Boulevard, Bird Rock, San Diego, California After

27. La Jolla Boulevard, Bird Rock, San Diego After

28. La Jolla Boulevard, Bird Rock, San Diego After

29. Roundabouts Benefits: Injuries and crashes reduced 90%
30% more traffic capacity
Gateway entry
Pedestrian-friendly
Low traffic speeds
Reduced noise
Reduced emissions
Reduced maintenance
Business-friendly

30. Roundabout design characteristics
Separated sidewalk to direct peds to crosswalks
Slow speed exit
Splitter island
Truck apron
Lots of deflection for slow speeds throughout
Crosswalk 1 car length back
Animated. The red line indicates the path a vehicle travels through a roundabout. Start at the upper left and read items counterclockwise. Click to animate the red line just before you get to the “Slow speed entry” item.
Urban roundabouts are designed for operating speeds of about MPH.
Slow speed entry with yield
Bend OR

31. Roundabouts are safer
32 vehicle-to- vehicle conflicts
24 vehicle-to- pedestrian conflicts
“Results of this study indicate that converting conventional intersections from stop sign or traffic signal control can produce substantial reductions in motor vehicle crashes.”
March 2000 Study by the
Insurance Institute for Highway Safety
Roundabouts improve safety at intersections by slowing the speed of vehicles and reducing the number of conflicts. The Institute of Highway Safety issued a report in 2000 that studied the impact of roundabouts on crashes and analyzed data from 24 intersections that were converted from stop sign or traffic signal control to roundabouts. The “before and after” study found reductions of 39 percent for all crash severities combined and 76 percent for all injury crashes. Reductions in the number of fatal and incapacitating injury crashes were estimated to be about 90 percent. The report concluded that “Results of this study indicate that converting conventional intersections from stop sign or traffic signal control can produce substantial reductions in motor vehicle crashes.”
8 vehicle-to-vehicle conflicts
8 vehicle-to- pedestrian conflicts

32. Before After One pedestrian fatality per year
Bradenton Beach, FL, Intersection of State Routes 684 and 789
After
Zero pedestrian fatalities in over 8 years
Roundabouts can serve as gateways and can help revitalize a neighborhood as was the case at this intersection on a state highway in Bradenton Beach, Florida which was claiming one pedestrian fatality every year. Since the roundabout was installed over eight years ago there have been no pedestrian fatalities.

33. Roundabouts and Pedestrians

34. 18 mph
18 mph

35. 14 feet
Grand Junction, Colorado

36. Sacramento, CA West River Drive and Orchard Lane

37. Sacramento, CA West River Drive and Orchard Lane

40. Roundabouts and Bicyclists

41. Montpelier, VT

43. University Place, WA

44. Davis, CA

45. Roundabouts, Trucks and Fire Departments

46. Petaluma, CA — Roundabout at Corona Road and Sonoma Mountain Parkway

47. Petaluma, CA — Roundabout at Corona Road and Sonoma Mountain Parkway
Fire Station #2, 1001 N. McDowell Blvd.
Petaluma, CA — Roundabout at Corona Road and Sonoma Mountain Parkway

48. Petaluma, CA — Roundabout at Corona Road and Sonoma Mountain Parkway
Mountable Curb for large trucks, emergency responders
Petaluma, CA — Roundabout at Corona Road and Sonoma Mountain Parkway

49. Mountable Curb can be used by large trucks, emergency responders
Fort Pierce, FL

50. Roundabout problems for blind pedestrians:
This slides explains the problems reported by blind pedestrians, especially at multi-lane roundabouts. Note it has some design flaws: the tangents allow drivers to exit at high speed.
Roundabout problems for blind pedestrians:
Circulating traffic masks the sound cues the blind use to identify gaps and masks the sound of yielding vehicles
Tangential circulating roadway, tangential exit => high speed (worse at 2-lane roundabouts)
Towson MD
8-50 50