Mountlake Terrace traffic report: volumes rebounded after 2020; several intersections identified as collision hot spots

City Traffic Engineer John Merrick presented the city’s 2024 annual traffic report to the Mountlake Terrace City Council, outlining traffic volumes, speeds and collision patterns and identifying specific corridors and intersections for follow-up work.

Merrick said the city’s analysis used traditional pneumatic tube counts, contracted field turning-movement studies and a new subscription service that aggregates anonymized smartphone and connected-vehicle data, allowing staff to look back to 2017 for street-level trends. He told council the data helped staff focus limited resources on corridors with the highest collision rates and potential for mitigation.

Merrick and Public Works Director Gary Schmick described three headline findings: traffic volumes fell sharply in 2020 and have been trending back up since; the portion of drivers traveling faster than most others rose during the low-volume pandemic period and has declined as volumes returned; and collisions remain concentrated on a few corridors. “We saw a pretty sharp reduction in volumes in 2020,” Merrick said, and added the new data source “lets us get traffic speed and volumes for any street in the city, going back to 2017.”

Key statistics Merrick cited from the report: 200 total recorded collisions in the city in the most recent 12‑month period; 60 injury collisions in 2024, up slightly from 58 the previous year; pedestrian collisions were low in recent years (two in the last year cited); bicycle collisions averaged roughly two to three per year; and historic peaks were higher — for example, 2015 recorded about 250 collisions. Merrick emphasized that fatal collisions remain rare (about one every other year) but that low counts make trend detection difficult.

The report maps and heat‑map analysis identified concentrated collision activity on the 200th Avenue corridor and at the 200th/12th/40th intersection complex. Merrick said the two 200th corridor segments together account for “a little over a third of all collisions in the city.” He also called out 40th Avenue near the high school as having high 85th‑percentile travel speeds on a posted 30‑mph segment, and noted that some arterials have 85th‑percentile speeds roughly 5 mph over posted limits.

Merrick described typical collision types and contributing conditions: angle collisions (turning) and rear‑end collisions make up more than half of crashes; collisions were more common on dry pavement and during daylight hours (when more people travel); and weekday afternoons and the 5–6 p.m. commute had the highest shares of collisions. He also presented a ten‑year breakdown showing years with lower volumes (2020) had higher measured speeds and, in at least one year, a higher count of injuries — a pattern Merrick said could reflect the relationship between speed and injury risk.

Council members pressed for details and next steps. Councilmember Woodard and others asked for a more granular look at 40th Avenue near the high school; Merrick agreed and said he would “take a closer look at to see what we, see if we can find some trends and things” for that corridor. Merrick also recommended a combined approach — engineering, enforcement and education — rather than relying on a single tactic.

On corridor interventions Merrick proposed several near‑term and longer‑term items the department will pursue or study: swapping some signal left‑turn indications to flashing yellow arrow operation to clarify yield behavior at left turns; striping left‑turn pockets on parts of 200th; continuing adaptive signal timing on the corridor between I‑5 and Aurora; and a detailed study of the multiway stop at 50th/220th to consider a roundabout or traffic circle. He noted that the 200th/12th/40th signal is operated by the City of Lynnwood and that coordination would be required for signal changes there.

Councilmembers also urged the department to map the delta between posted speed and measured travel speed across the entire city, to produce origin‑destination flow maps if budget permits, and to make pedestrian and bicycle collision locations more visible on a separate map for grant‑making and infrastructure prioritization. Merrick said staff will follow up with more location‑specific analysis and will bring recommendations and potential low‑cost measures back to council for funding consideration.

The presentation and council discussion also touched on regional work: Councilmember Murray noted the Puget Sound Regional Council’s recently adopted Regional Safety Action Plan and asked staff to align local analytics and local grant applications with regional funding opportunities. Merrick and staff said the new data tools and the report will help the city prepare competitive grant applications.

Staff framed the report as an information and prioritization tool rather than a directive for immediate construction; Merrick said the report will inform the six‑year CIP and staffing requests, and that specific capital improvements will return to council as formal project proposals and funding actions.

Merrick closed by proposing staff follow‑up actions and requesting council direction on any high‑priority locations. Councilmembers encouraged immediate follow up on 40th Avenue near the high school and the 200th corridor locations shown in the heat map.