Regional Signal Timing Plans
Studies
The Bipartisan Infrastructure Bill (BIL) established the Carbon Reduction Program (CRP), a new regionally competitive grant program managed by RTC. The CRP authorizes grant funding for projects designed to reduce transportation emissions. RTC was awarded funds to develop signal timing to improve traffic flow, safety, and air quality in the Clark county urban area. RTC in coordination with local agencies in Clark County, Washington and our consultant will develop regional signal timing plans along major corridors in Clark County.
Benefits of re-timing Traffic Signals
Decreased Vehicle Emissions – The reduction in idling time for vehicles reduces the amount of emissions that enter the atmosphere. Vehicles emissions include the following products: nitrogen oxides, volatile organic compounds, carbon dioxide, particulate matter, and sulfur dioxide. Reduction of these emissions improves the environment and air quality for all citizens.
Shortened Travel Time – Retiming signals can reduce the amount of time and number of times drivers are stopped at a red light through a corridor. The reduction in stops allows drivers to travel through the corridor in less time.
Reduced Fuel Consumption – A reduction in fuel consumption is realized as the amount of time vehicles spend idling is reduced. The reduction in fuel consumption saves drivers money by decreasing fuel usage.
Increased Safety – Improved signal operations not only leads to benefits in congestion, fuel economy, and air quality as described above, but it can also reduce crashes. According to the Federal Highway Administration, providing improved signal coordination on a corridor can reduce crashes by 15%.
Increased Travel Time Reliability – The reduction in congestion and decrease in crashes will contribute to a more reliable driving experience meaning driving along the corridor will, in general, be more similar from day-to-day. Travel time reliability is not only important to commuters but commercial/ freight traffic as well.
Regional Signals Timing Plans
Major tasks include prioritize corridors; review/update traffic signal timings; deploy signal timings, and produce reports. Corridors being evaluated and prioritized include congestion management corridors.
Corridors
Corridors being evaluated and prioritized include congestion management corridors. The RTC Congestion Management Process (CMP) corridors were used as the basis for corridor identification. The below figure provides a map of the non-freeway CMP corridors and traffic signal locations in the region.
The table below lists the 28 CMP corridors in order of prioritization. The VAST/TSMO Steering Committee. The VAST Steering Committee prioritized the CMP corridors using the performance metrics and weighting factors identified in the Corridor Prioritization Memo FINAL(PDF, 383KB).
TABLE 1: CORRIDORS BEING EVALUATED
Text versionof the table of evaluated corridors follows:
Corridor Ranking
1-SR 503 South (from 119th St to Fourth Plain/SR 500)
2-Mill Plain East (from I-205 to 192nd Ave)
3-112th Chkalov Gher from SR 500 to Mill Plain
4-Fourth Plain West (from I-5 to Andresen Rd)
5-162nd/164th Ave South (from Mill Plain to SR 14)
6-Fourth Plain East (from SR 503 (117th Ave) to 162nd Ave)
7-18th St (from 112th Ave to 162nd Ave)
8-Main Street (from Ross St to Mill Plain)
9-HWY 99 (from 139th St to Ross St)
10-SR 503 North (from SR 502 to 119th st)
11-136th/ 137th/ 138th Ave (from Padden Pkwy to Mill Plain)
12-Mill Plain West (from I-5 to I-205)
13-Andresen/ 72nd North (from 119th St to SR 500)
14-162nd/ 164th Ave North (from Ward Rd to Mill Plain)
15-Andresen South (from SR 500 to Mill Plain)
16-28th St (from Andresen Rd to 162nd Ave)
17-139th St (from NW 36th St to NE 29th Ave)
18-78th/76th St (from Lakeshore Ave to SR 503 (117th Ave))
19-99th St (from Lakeshore Ave to St John Rd)
20-Fourth Plain Central (from Andresen Rd to SR 503 (117th Ave))
21-192nd Ave (from SE 1st St to SR 14)
22-Mill Plain/SR 501 (from Fourth Plain to I-5)
23-134th St/Tenne/Salmon Creek Ave from NE 139th St to NE 50th Ave
24-SR 502 (from I-5 to SR 503)
25-Padden Parkway (from 78th St to 162nd Ave)
26-Hazel Dell (from Hwy 99 to 63rd St)
27-St. Johns/St. James/Fort Vancouver Way (from NE 72nd Ave to Mill Plain)
28-Fourth Plain/SR 501 (from NW Lower River Rd to I-5)
Corridor Prioritization Methodology
This section describes the methodology to evaluate the existing corridor performance and prioritize the corridors for the signal coordination efforts. As mentioned in the previous section, CMP corridors and key urban corridors confirmed by VAST TSMO Steering Committee members were used as the initial list of corridors considered for this project. A three-step approach was used to prioritize the needs for updating the traffic signal timing plans for the County’s urban corridors. To prioritize the corridors, a screening criteria/process was developed, which includes evaluation criteria such as mobility, safety, delay, transit utilization, and travel time reliability. Each of the steps are described in the subsections below.
1. Evaluate the corridor performance based on historical data.
2. Develop a weighting scheme and corridor ranking.
3. Obtain agency input on additional information and identify the set of corridors to be re-timed.
Pilot Corridors - Phase 1 (2025)
As part of phase 1, seven non-freeway corridors from the RTC Congestion Management Process corridors were selected through a prioritization process to develop and apply updated signal timing strategies based on existing conditions and regional goals (see Figure). The selected corridors represent key routes where signal optimization and coordination has potential to provide meaningful benefits. A detailed technical report and a public-facing cutsheet were prepared for each corridor to summarize recommended timing plans and key findings.
Pilot Corridors - Phase 2 (2026)
As part of phase 2, two prioritized non-freeway corridors from the RTC Congestion Management corridors were selected for updated signal timing (Andresen Road and Burton Road). In phase 2, Artificial Intelligence (AI) software was tested against standard signal timing method to test viability of utilizing AI for signal timing. Corridor signal timings were updated in October of 2026, and findings will be added to the website by the end of the 2026 calendar year.
PILOT CORRIDORS FOR IMPROVEMENT
- SR-503 South (119th Street to Fourth Plain Boulevard)
- Mill Plain Boulevard (104th Avenue to 192nd Avenue)
- Fourth Plain Boulevard East (SR-503 to 162nd Avenue)
- 162nd/164th South (SR-14 to mill Plain Boulevard)
- 18th Street (I-205 NB Ramp to 162nd Avenue)
- SR-503 North (119th Street to 244th Street)
- 162nd/164th North (Mill Plain Boulevard to 78th Street)
- Andresen Road (NE 18th Street to NE 63rd Street)
- Burton Road (Andresen Road to NE 162nd Avenue)
Before/After Report Cutsheets
- SR503 South Cutsheet (PDF, 2MB)
- Mill Plain East Cutsheet (PDF, 2MB)
- Fourth Plain Cutsheet (PDF, 1MB)
- 162nd/164 South Cutsheet (PDF, 2MB)
- 18th Street Cutsheet (PDF, 1MB)
- SR503 North Cutsheet (PDF, 2MB)
- 162nd_164th North Cutsheet (PDF, 2MB)
Findings
Updated signal timing plans demonstrated meaningful benefits across the seven corridors and aligned well with the project goals of improving traffic flow, air quality, and safety. The overall results show better coordination with shorter travel times, fewer stops, and lower emissions, along with operational improvements that support safety across the study corridors.
Downloads
Corridor Prioritization Memo FINAL (PDF, 383KB)
SR 503 South Before/After Report (PDF, 2MB)
Mill Plain East Before/After Report (PDF, 2MB)
Fourth Plain Blvd East Before/After Report (PDF, 1MB)
162nd/164 South Before/After Report (PDF, 2MB)
18th Street Before/After Report (PDF, 1MB)
SR503 North Performance Summary Report (PDF, 2MB)
162nd/164th North Before/After Report (PDF, 2MB)
Staff Contact
Judith Perez Keniston, AICP
P. 564.367.5231
E.