1) Seattle has implemented over 30 road diets since 1972 which reduce vehicle lanes to calm traffic and accommodate other modes. 2) Road diets in Seattle have been shown to reduce speeds and collisions while increasing safety for pedestrians and bicyclists. They have also maintained traffic flow. 3) Seattle identifies road diet candidates based on safety and livability factors then implements designs considering transit, parking, turning movements and other details. Outreach addresses common concerns around traffic impacts.

1. Road Diets: The Seattle Experience
Pro Walk / Pro Bike: Pro Place
September 11, 2012
Brian Dougherty
Carol McMahan

2. Where is Seattle?

3. Complete Streets
• 16% of households do not
have a car
• Seniors
• Youth
• Safety
• Transit riders
Ultimately, we all need
complete streets

4. Seattle’s Complete Streets Approach
• Vision: Streets that are • Implementation: Complete
safe, convenient and Streets checklist
accessible for everyone
• Outreach: Community
• Plans: Bicycle, Pedestrian, collaboration
Transit, Freight
• Opportunities: Redesigning
• Funding: Bridging the Gap, city streets
state, federal grants

5. For whom road diets might apply
• ADT < 15,000 OK
• ADT 15,000 - 20,000 Evaluate
• ADT >20,000 Maybe
Small Cities Large Cities
Towns Suburbs

6. Why Road Diets?

10. Complete Streets Approach

11. Economic Benefits

12. Economic Benefits

13. Why Road Diets? Fewer Collisions
US Federal Highway Administration Proven Safety
Measure to reduce all collisions by 29%
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14. Why Road Diets? Pedestrian Safety
A modest decrease in motor vehicle
speed can dramatically increase
survival in pedestrian crashes
Speed
reduction from
40 to 30
increases
survival rate by
5x

15. Seattle Road Diet History
14
12
10
8
Miles
6
Projects
4
2
0
1972 - 1979 - 1986 - 1993 - 2000 - 2007 -
1978 1985 1992 1999 2006 2012

16. Seattle Road Diet History
• 34 road diets have been
installed in Seattle since
1972
• 1972 – 2006: 21 Projects
• 2007 – 2012: 13 Projects

17. How are Corridors Identified?
• Complete Streets for
capital projects
• Bicycle Master Plan
• Pedestrian Master Plan
• Community requests for
neighborhood plan
implementation S Columbian Way

18. What Factors are Considered?
Tier 1: Traffic Operations
Before After Nickerson St

19. What Factors are Considered?
Tier 2: Safety/Collisions
Before After N 130th St (2010)

20. What Factors are Considered?
Tier 3: Livability
Before After 7th Ave (2010)

21. Don’t Forget the Design Details
•Freight
•Lane width
•Turning movements
•Transit
•Lane width
•Turning movements
•Stop consolidation
•Trolley lines

22. Don’t Forget the Design Details
• Parking
– Peak hour
– Utilization

23. Don’t Forget the Design Details
• Pedestrian crossings
– Refuge islands
– Marked crosswalks

24. Don’t Forget the Design Details
• Signals
– Detection
– Optimize corridor

25. Don’t Forget the Design Details
• Pavement Condition
Spot repair

26. Out Reach: Common Concerns
• There will be gridlock!
– Maintain capacity at signalized intersections
– Gain efficiency by removing left turns from travel lanes
• People will cut though the neighborhood!
– Monitor pre and post project implementation
– Implement traffic calming measures if problems occur
• I’ll be trapped in my driveway by all the traffic!
– Sight distance is improved for left turns
– Access from side streets and driveways improved by
crossing only one travel lane to the two-way left turn lane.

27. Out Reach: Common Concerns
Street Before After Requests to
Comments Comments remove
NE 125th St 394 7 3
Nickerson St 66 8 0

28. Pitfalls
Carolina Beach, North Carolina

29. Before & After Studies
Data needs Before Study After Study (>1 year)
ADT √ √
Bike and Ped Counts √ √
Crash Data √ √
Speed √ √
Transit Operations √ √
Turning vehicle counts √ √
Gap Studies √ √
Parking use √ √
Side street diversion √ √
Vehicle Classification √ √
Resident Satisfaction √ √
Business Satisfaction √ √

30. Case Study: Stone Way N
• 1.2 miles
• ADT – 13,000
• Burke-Gilman Trail Access
• Woodland Park Access
• Within 5 blocks – 8 schools, 2
libraries and 5 parks

31. Stone Way N: Marked Crosswalks
• Uncontrolled, marked
crosswalks at 4
intersections.
• Crosswalk guidelines
changed in 2004.
• Marked crosswalks would
be non-compliant with
four-lane cross section.

32. Stone Way N: Bicycle Master Plan
• Adopted in 2007.
• Stone one of the first
projects completed under
the plan.
• Recommended climbing
lane and sharrow.

33. Stone Way N: 85th Percentile Speed
• Speed limit 30
• 85th percentile was 37
mph prior to
rechannelization
• Dropped to 36 mph
northbound
• Dropped to 34 mph
soundbound

34. Stone Way N: Aggressive Speeders
• 3% of vehicles traveled at
40 mph+ prior to
rechannelization
• Fewer than 1% traveled
at 40mph+ after
rechannelization
• Reducing the number of
top speeders greatly
reduces seriousness of
collisions and injuries.

35. Stone Way N: Bicycle Volume
• Increased 35%
• Represents almost 15%
of the peak hour traffic
volume!

36. Stone Way N: Motor Vehicle Volume
• ADT Dropped 6%
(consistent with citywide
trend between 2006-08)
• Peak Hour volume
dropped approximately
5%
• Off-peak volume actually
increased south of 45th
Street

37. Stone Way N: Neighborhood Traffic
• Four non-arterial streets
commonly mentioned as
alternatives to Stone
• Volume decreased on all
four of those streets
• Traffic did not divert after
rechannelization.

38. Stone Way N: Collisions
• Total collisions declined
14%
• Injury collisions declined
33%
• Angle collisions declined
56%
• Bicycle collisions no
change, but rate declined
• Pedestrian collisions
declined 80%

39. Stone Way N: Conclusions
• Speed has declined
• Collisions have declined
• Pedestrian crossings are
safer
• Bicycle volume has
increased
• Traffic has not diverted to
neighborhood streets
• Peak hour capacity has
been maintained
• Strong case for
implementing road diets

40. Possible Elements of Future Studies
Study Data: To Address/Answer:
• Pre and Post survey • Livability
of nearby businesses • Impact to business
and residents • Travel time
• Traffic signal LOS • Diversions to other
• Volume of parallel arterial streets
arterials

41. Follow-up studies and monitoring
• Volume of principal street
/peak hour capacity
• Speed and collisions
• Traffic signal level of service
• Volume of parallel arterials
• Travel time
• Bicycle volumes
Stone Way

42. NE 125th St
Factors:
• ADT 16,200
• 4 lanes to 2 lanes
with TWLTL and bike
lanes
• Business district
• High bus usage
• High number of
pedestrian collisions
Before

43. NE 125th Street
Before After

44. NE 125th St
Volume
ADT AM PM
4% 6% 12%
Speed
85th% OVER TOP
-8%
30 END
-12% -69%

45. Nickerson St:
Before After

46. Nickerson Case Study
Before

47. Nickerson Case Study
After

48. Columbian Way Complete Street
• ADT 11,200
• Repave project
• 4 lanes to 2 lanes
with TWLTL and bike
lanes
• New sidewalks

49. Recent Results
Street ADT ADT Collisions 85th % Top end Travel
begin change speeders time
Stone Way 13,000 -6% - 14% - 6% - 80% N/A
+ 1.5
NE 125th St 16,200 + 4% N/A - 8% - 69%
min
Nickerson St 18,600 - 1% - 23% - 21% - 94% N/A
Columbian
11,200 + 20% No change - 6% -50% N/A
Way

50. Not the end of the story: Dexter Ave N
Before After

51. Not the end of the story: Dexter Ave N
Before After

52. Just Completed: S Othello Street
Before After

53. Additional Resources
• Nickerson Street Before and After Study
– http://www.seattle.gov/transportation/nickerson.htm
• Stone Way Before and After Study
– http://www.seattle.gov/transportation/docs/StoneWaybeforeafterFINAL.pdf
• FHWA: Proven Safety Countermeasures
– http://safety.fhwa.dot.gov/provencountermeasures/index.htm
• NACTO Guides
– http://nacto.org/
• National Complete Streets Coalition
– http://www.completestreets.org/
•