SE Clinton, 12th to 21st Avenue
CLINTON BIKEWAY
12th AVENUE TO 21th ANVENUE
12th AVENUE TO 21th ANVENUE
Final Project Evaluation
Introduction
Portland’s Bike Program enlisted the help of the
Traffic Calming section for a speed bump project in the spring of 1998. Speed
bumps were identified by local citizens as the most appropriate tool to address
traffic problems along the project segment of SE Clinton, 12th to
21st Avenues.
The goal of the project was to enhance street
safety for bicycle riders by reducing the 85th percentile speed of vehicles
using SE Clinton closer to the legal maximum speed limit of 25 miles per hour
(mph). Speed bumps have proven to be effective tools to reduce vehicle speed
without affecting access. It is not an intended goal to reduce traffic volume on
low-volume Local Service Streets.
SE Clinton, from 12th to
21st Avenues, serves a mixed single family residence and commercial
neighborhood. SE 12th Avenue, to the west, is a Major City Traffic
street under Portland’s traffic street classification system. SE 21st
Avenue, at this project segment's east end, is a Local Service street. Clinton
was broken at 21st as a project segment due to Tri-Met bus service
between 21st and 26th Avenue. SE Clinton, from
12th to 21st Avenue, is fairly level, is straight, except
for a slight jog at 19th, and has parking, sidewalk and curb on both
sides.
Open House
Residents along SE Clinton were invited to an
open house June 3, 1998 to review and comment on the proposed speed bump
installation. Fourty-five people attended the open house. Most of those who
attended expressed approval for the proposed project. Some considered the bumps
to be excessive, or inadequate, while others expressed concern over noise and
bump location. A petition was available at the open house for residents along SE
Clinton, from 12th to 21st Avenues, to sign and was
circulated after the open house by a local resident. Petition results were as
follows:
|
Category |
Number |
Percent of Total |
|
Yes |
39 |
69.6% |
|
No |
17 |
30.3% |
|
Total |
56 |
100% |
Performance
Five 14-foot speed bumps, at 400 to 530 foot spacing, were
constructed along the 0.44-mile length of SE Clinton, from 12th to
21st Avenues, on September 26, 1998 by Portland’s Bureau of
Maintenance.
Vehicle Speeds
As graph one (next page) shows, vehicle speeds that
previously peaked at 26 to 28 mphs now peak between 20 to 25 mphs. The average
85th percentile vehicle speed before the project was 33 mph. Since bump
construction the average 85th percentile speed is 24.9 mph and ranges from a low
of 18 mph (near a bump) to a high of 27 mph in the 25-mph zone. Before
installation of the speed bumps 80% of drivers exceeded the posted speed limit
of 25 mph and 10% exceeded the limit by 10 mph or more. Since bump construction
12% of drivers exceed the posted speed limit and 0.24% exceed the limit by 10
mph or more.
Graph 1
Traffic Volume
Traffic volumes measured before bump construction averaged
3400 vehicles per day (vpd). After bump construction volumes averaged 2300 vpd
and varied from 2000 to 2700 vpd. This represents a 30% reduction, well above
normal daily fluctuations. Traffic volumes measured on streets adjacent to SE
Clinton, 12th to 21st Avenue, no significant increases
from measurements before construction.
Conclusion
Traffic Calming on SE Clinton, 12th to
21st Avenues, has successfully reduced the average 85th percentile
speed closer to the posted speed and also decreased the number of cars using the
street.