One of the key results of the extensive six-year public planning to revitalize North City and improve traffic safety was the decision to put 15th Ave. NE on a “road diet”, reducing it from four-lanes to three. While seeming counter-intuitive, such conversions have been successful regionally and nationally in improving pedestrian and motorist safety, revitalizing neighborhood economies, and improving quality of life.
The problem is that four-lane roads frequently generate excess speeds. Since motorists notice that there are spare lanes they drive faster than they should and change lanes frequently, especially during rush hour when frequent right- and left-turn movements occur, which slow lane speed. Last minute, instant lane swapping occurs leading to rear-end crashes and failure to see pedestrians.
Traffic engineering studies indicate that four-lane roads carrying up to 25,000 vehicles per day (average daily traffic) are good candidates for “road diets”. Since 15th Ave. NE carries an average of 17,000 to 19,000 vehicles per day, had pre-conversion speeds in excess of 39-mph (at the 85th percentile – a standard traffic measure), a history of serious pedestrian accidents, and a commercial area ready for revitalization, this corridor was an ideal candidate for conversion.
Last year the section between 175th and 150th was converted to three-lanes and the business district portion from just north of NE 180th to NE 175th is scheduled to be converted as part of the North City improvement project. The three-lane conversion will also extend north to approximately 24th Ave. NE to serve as a transition into the business district.
Some of the reasons for conversion are:
Safety – A three-lane roadway operates in a safer manner for several reasons:
- Lower Speeds – Reducing the number of lanes in one direction from two to one results in lower speeds overall. Faster drivers are forced to drive the same speed as the slower vehicles in front of them. Conversion to three-lanes on 15th Ave. NE has reduced average speeds by 2% over the past year, bringing speeds closer to the posted 35-mph limit.
- Reduction in Rear-End Collisions – Vehicles looking for a gap in traffic to make left-turns now have a space to wait outside of the higher-speed through-traffic lanes and are crossing only one lane of on-coming traffic.
- Safer Crosswalks – Changing the number of lanes from two to one reduces the “multiple threat” scenario for pedestrians, where a vehicle in one lane stops and a vehicle in the adjacent lane does not. The stopped vehicle often blocks visibility of the pedestrian as they are crossing. This was a factor in the Tia Townsend fatality, a child struck in the crosswalk on 15th Ave. NE at 170th on March 28, 2002.
Capacity – At first glance, it would seem that removing travel lanes from a street would create congestion due to a loss in the capacity of the street to carry cars. But what we forget is that during rush hour, the inside lanes of a four-lane street are generally used as a left-turn lane and therefore are frequently blocked for use as a through lane. As such, only the curb lane can handle most through trips if the street has no left-turn lane. Consequently, a three-lane street with a left-turn lane handles about the same number of vehicles as a four-lane street. In fact, studies show that four-lane and three-lane streets carry about the same number of vehicles.
The average daily volume on 15th Ave. NE was 16,635 in March of 2003 compared to 16,045 in February/March of 2004 (within expectations for sampling fluctuations), indicating no loss of capacity after conversion.
Travel Time – Average travel times on four- to three-lane conversions does not decrease significantly, and even improves sometimes, due to the dedicated left-turn lane.
Cut Through Traffic – A concern of residents near 15th Ave. NE was that the conversion would force cars to seek faster routes by cutting through nearby residential streets. Traffic counts over this past year have shown no significant shifts to nearby streets. The City’s traffic division continues to monitor traffic flows and has funds set aside to install traffic calming measures to mitigate cut-through traffic if it becomes a problem.
Cross Traffic – The planned installation of a new traffic signal at 150th and enhanced timing of signals will also help create more regular gaps for traffic crossing or entering 15th Ave. NE.
Quality of Life – Another key component to the long awaited North City Plan is the creation of a pedestrian friendly, safe, “Main Street” commercial district, with slower speeds, attractive sidewalks, landscaping, underground utilities, street lighting and other amenities that encourage civic pride and new investment. Bringing new buildings closer to the sidewalk and narrowing the street to three-lanes are crucial components of this community-created vision. Already new business such as the Hotwire Coffee House and a new 88-unit apartment complex have been attracted to North City as a direct result of the North City Plan.
The improvements to North City and 15th Ave. NE are the culmination of years of citizen effort starting before incorporation in 1995. Extensive public meetings on the Comprehensive Plan, North City Sub Area Plan and on the North City design resulted in a final design for North City and 15 Ave. NE. On Aug. 23 the City Council will consider options for awarding the bid for the North City Business District improvements to bring this long awaited project to reality.
For more details and examples, see Road Diets - Fixing the Big Roads.
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