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NE 21st/24th Avenue, Knott to Ridgewood

Final Project Evaluation

Introduction

The Traffic Calming Program (TCP) undertook a traffic calming project in the fall of 1993 to address traffic problems identified by residents along NE 21/24th Avenues from Knott to Ridgewood.

Map

 
NE 21/24th Avenues serve a single family residence neighborhood. NE 24th Avenue has a small commercial center at NE Fremont Street. NE Knott Street, to the south, is a Local Service street. NE Ridgewood , at NE 21st Avenue's north end, is a Local Service street. NE Fremont Street , at NE 24th Avenue's north end, is a Neighborhood Collector street. NE 21/24th Avenues are fully improved. A large portion of the daily traffic on NE 21/24th Avenue is believed to be due to a lack of nearby north-south Collector streets.
The traffic committee's adopted goals and objectives were as follows:

I. DECREASE SPEEDING ON BOTH STREETS:
A. 85th percentile of drivers should travel at or below 30 mph.
B. Drivers should travel at a constant speed reducing acceleration/deceleration.
C. Reduce speeds at the intersection of 21st/24th and Fremont.
D. Reduce speeds at Madeleine School crosswalks (at 24th/Siskiyou, 24th/Klickitat and 21st/Siskiyou.)
II. IMPROVE SAFETY FOR PEDESTRIANS:
A. Reduce exposure of children to hazard by reducing the amount of time they walk in the street at crosswalks or by slowing down drivers.
B. Increase pedestrian safety on 21st at Fremont, Alameda.
C. Define crossing area at 21st/Regents.
III. MINIMIZE NEGATIVE IMPACT ON BICYCLES:
 
To meet the above goals, the committee developed the following proposals:
I. Install speed bumps on NE 21st and 24th to slow down speeding drivers.
II. Construct curb extensions at crosswalks to improve pedestrian safety.
III. Realign the intersection of NE 21st and Regents to improve safety.

Open House
 
All residents along NE 21/24th Avenue were invited to an open house to review and comment on the proposed speed bump installation. As required by the TCP process, a mail ballot was conducted by the Bureau of Traffic Management. Almost 50% of the ballots mailed out were returned, and a majority of the ballots returned were in favor of the project. Eligible voters included all residents, businesses and property owners within the area likely to receive significant benefits or disadvantages from the project. A breakdown of the vote is shown below.
 
NE 21st/24th AVENUE TCP BALLOT RESULTS
 
  Total Owner Occupants Renters Nonresident Owners
Valid Ballots: 626 507 67 56
Ballots Returned: 309 287 9 13
Percent Returned: 49.4% 56.6% 13.4% 23.2%
Number of Yes Votes: 214 197 8 10
Number of No Votes: 95 90 1 3
% of Votes in Favor: 69.3% 68.6% 89.0% 77.0%

NE 21st AVENUE - Knott to Ridgewood

Construction

Five 22-foot speed bumps, at 480 to 550 foot spacing, were constructed along the 0.6 mile length of NE 21st Avenue, Knott to Ridgewood, on April 2, 1995 by the Bureau of Maintenance. The curb extensions, at 21st and Siskiyou, and the intersection re-alignment at 21st and Regents were completed October 23, 1996.

 
Performance
 
 
 
Vehicle Speeds
 
As the graphs shows, vehicle speeds have been shifted into the range of 26 to 31 mph.   The average 85th percentile vehicle speed before the project was 33 mph. Since bump construction the average 85th percentile speed is 30 mph and ranges from a low of 24 mph (near the bumps) to a high of 33 mph. Before installation of the speed bumps an average of 80% of drivers exceeded the posted speed limit of 25 mph and 14% exceeded the limit by 10 mph or more. Since bump construction 58 % of drivers exceed the posted speed limit and only 3% exceed the limit by 10 mph or more.
 
Traffic Volume
 
Traffic volumes measured on NE 21st Avenue before bump construction averaged 3700 vehicles per day (vpd) and varied from 2000 to 5000 vpd. The vehicle volumes tend to increase near the south end of the project. Traffic volumes measured after project completion show no significant changes from volumes measured prior to construction.

NE 24TH AVENUE - Knott to Fremont

Construction
 
Three 22-foot speed bumps, at 570 to 600 foot spacing, were constructed along the 0.4 mile length of NE 24th Avenue, Knott to Ridgewood, on April 2, 1995 by the Bureau of Maintenance. The curb extensions, at 24th and Siskiyou and at 24th and Klickitat were completed October 23, 1996.
 
Performance
 
 
Vehicle Speeds
As the graph shows, vehicle speeds, previously concentrated between 26 and 34 mph, have been shifted into the range of 23 to 31 mph. The average 85th percentile vehicle speed before the project was 32 mph. Since bump construction the average 85th percentile speed is 31 mph and ranges from a low of 25 mph (near the bumps) to a high of 32 mph. Before installation of the speed bumps an average of 73% of drivers exceeded the posted speed limit of 25 mph and 8.5% exceeded the limit by 10 mph or more. Since bump construction 45% of drivers exceed the posted speed limit and only 1.4% exceed the limit by 10 mph or more.
 
Traffic Volume
 
Traffic volumes measured before bump construction averaged 2800 vehicles per day (vpd) and varied from 2600 to 3000 vpd. After bump construction volumes averaged 2400 vpd and vary from 1200 to 3100 vpd. Traffic volumes on NE 24th Avenue follow the same pattern as those on NE 21st Avenue, increasing to the south.

Neighborhood

Traffic Volume
 
Traffic volumes measured on side streets adjacent to NE 21/24th Avenue showed no significant increases from volumes measured prior to speed bump construction.
 
Table 1. Neighborhood Volume Changes
 
  North of Knott South of Fremont North of Fremont
Street Before After % Change Before After % Change Before After % Change
19th Avenue na na na na na na 261 462 +76.8
20th Avenue 239 319 +33.5 179 201 +12.3 180 247 +36.9
Regents na na na na na na 1553 1430 -7.9
21st Avenue 5139 4658 -9.4 4770 3819 -19.9 2467 2238 -9.3
22nd Avenue 228 307 +34.6 223 296 +32.7 209 129 -38.3
23rd Avenue 218 279 +27.8 354 355 +0.1 112 155 +38.4
24th Avenue 2892 2728 -5.7 2667 2569 -3.7 1178 1224 +3.9
25th Avenue 246 360 +46.3 333 359 +7.8 189 199 +5.3
26th Avenue na na na 405 393 -3.0 329 479 +45.7
Totals 8962 8651 -3.4 8931 7992 -10.5 6478 6563 +1.3
na - not available

Conclusions

The 21/24 Traffic Calming Project has succeeded in meeting its primary goals as follows:
 
Decrease Speeding on Both Streets: Northeast 21st Avenue has had the greater reduction in average 85th percentile speed, 31 mph from 33 mph. Northeast 24th Avenue's 85th percentile speed has remained steady. More notable is the higher speed vehicles have been greatly reduced. The speed bumps did not cause any major shift of the vehicle traffic volumes into the surrounding neighborhood. Northeast 19th Avenue, north of Fremont, will continue to be monitored due to the high vehicle volumes measured there.
 
Improve Safety for Pedestrians: Crossings for Madeleine School have been treated with curb extensions to reduce the crossing distance and improve visibility of pedestrians.
 
Minimize Negative Impact on Bicycles: None of the improvements constructed interfere with a cyclist's ability to use the streets.
Traffic Calming on NE 21/24th Avenue, Knott to Ridgewood has enhanced street safety and livability.