Washington County Improves the Commute with Bluemac
- More than 120 roadside Bluemacs
- Bluetooth Classic capture rates greater than 10%
- Easy install & maintenance in signal cabinets
- Quantify signal timing & project improvements!
Washington County, Oregon is a county just west of Portland with an interesting mix of fast growing urban areas combined with bucolic rural environs, composed of about 1200 miles of centerline road.
Washington County Traffic Engineering faces many challenges in their day-to-day operations and planning endeavors, and certainly one is ever increasing congestion outpacing infrastructure improvement. Signal timing on key corridors is a recurring source of citizen complaints, complicated by the corridors crossing multiple jurisdictions.
Stacy Shetler, Washington County’s Principal Traffic Engineer, along with Shaun Quayle, Professional Transportation Engineer, decided to attack this problem in 2016.
Mr. Quayle’s perspective represented the team’s forward-thinking view: “We found ourselves asking if we can have a data-based discussion regarding congestion that makes sense to our citizens? Even better, can the transportation engineering team be proactive in communicating this information to the public?”
When looking at approaches to address this area, Mr. Shetler noted: “We needed a means that could provide us the core travel time data to quantify congestion, identify key bottlenecks, and use the data to improve performance in key links.”
Both Mr. Shetler and Mr. Quayle were familiar with Bluetooth® probe technology, and saw it as a great tool to help. Bluetooth is intended to be a short-range radio communication means between devices. It comes with different classes of range, rated all the way from 3 to 300 feet. Most devices fall into the 30 to 300 feet classes. Using Bluetooth offers a means to track a device which is not tied to a person, providing a high degree of anonymity. In his work for the City of Portland, Mr. Quayle measured vehicle capture rates typically greater than 10%, more than sufficient for the target corridors in Washington County.
Bluetooth was well suited to Washington County’s situation enabling them to set up data collection specific to the key corridors functioning 24x7x365 independent of weather conditions, while logging data in a means protecting citizen privacy. One reason the Bluemac system was chosen is it offered deep access to the underlying data and analytics, combined with a choice of different device configurations for effective installation into available locations (from inside signal cabinets to completely standalone and self-powered, connected to hardwired networks or independent data delivery via cellular).
Washington County addressed a few key challenges – being able to install into equipment owned by a different agency to complete data gathering for key corridors, as well as effectively share the data with other agencies to strive for a cross-agency view of congestion conditions in the wider Portland metropolitan area. The data and analytics produced by the Bluemac system could feed traffic planners with invaluable Origin-Designation reporting and a wide range of travel time analysis for planning work and model calibration, also easily making it available to consultants.
Figure 1: Bluemac Bluetooth probe mounted in a signal controller cabinet with a specially designed external antenna.
The system quickly demonstrated value in helping to address recurring citizen complaints along a major commute corridor – Scholls Ferry Road, regarding congestion during the AM peak commute period.
Figure 2: Scholls Ferry Road in Washington County.
Using Bluemac Site Services, Washington County was very quickly able to identify the bottleneck – between 121st Avenue and Nimbus Road.
Figure 3: The bottleneck on Scholls Ferry Road.
Via the built-in Origin-Destination analysis it turned out the majority of the traffic was coming from residential areas feeding into the core roads during the commute spanning two different signal networks, with one of those Washington County’s network.
Based on analyzing the data and applying their traffic engineering expertise, they came up with several signal timing strategies to test on their network, while using the Bluemac system to quantify changes in performance compared to the previous signal timing implementation. It turned out that setting up 30 seconds of additional green time on Scholls Ferry Road pushed much more traffic through, which of course meant the side streets with minor traffic had to wait an extra 30 seconds.
Figure 4: Comparative Overlay showing before (in red) and after (in blue) for signal timing changes on Scholls Ferry Road during the morning commute.
The change in performance was striking. Using Bluemac’s Comparative Overlay feature, the segment’s performance before the timing change at its worst was 350 seconds of average travel time, versus an estimated free flow travel time of just over 60 seconds. The new signal timing plan kept travel time under 150 seconds during the morning commute window!
But the segment can’t be looked at in isolation – it was important to have a route view across multiple segments. With Washington County’s well thought out Bluemac deployment, they were covered. The team used Bluemac Site Services to create a route using the readers they had set up along Scholls Ferry Road to look at the before and after travel time data.
Figure 5: Travel time stack up for the Scholls Ferry route BEFORE the signal timing changes – note it is on a scale of 1,000 seconds.
Figure 6: Travel time stack up for the Scholls Ferry route AFTER the signal timing changes – note it is on a scale of 600 seconds.
The route travel time stack up makes it easy to see where delay is happening along the corridor with the before and after. In the before condition Washington County saw at worst an average travel time for the route of 870 seconds, which decreased by 345 seconds to 525 seconds using the new signal timing plan! By looking at the median between the two timing plans, just under 3.5 minutes of travel time was saved for the morning commute. From a reliability perspective, the standard deviation decreased from 173 to 64 seconds, with a corresponding decrease in the 15th/85th percentiles – overall reliability is much better with the new timing plan.
Washington County has a distinct peak period during the morning commute from 7:15AM to 8:15AM – with Bluemac Site Services it is easy to look at that specific time period to compare the before and after, where they discovered an additional 3 minutes was saved, resulting in a total time savings for the route of 6.5 minutes using the new timing plan.
All for just 30 seconds of additional green time. Using the resulting analysis, Washington County can quantitatively demonstrate improving travel time during the key commute period, also proving useful for addressing any complaints from citizens waiting longer on side streets – they can certainly appreciate the trade-off of saving minutes on Scholls Ferry Road for an additional 30 second wait.
With their more than 120 Bluemac devices continuously logging data, Washington County is building a richer set of travel time and Origin-Destination data they are finding increasingly useful for daily operations and planning work. Via Bluemac Site Services, they provide access to other agency partners as well as consultants that are doing work for the County, the system makes it easy and flexible to securely work with the data and Site Services.
Figure 7: The Washington County BlueMAC deployment.
As part of Washington County’s contribution to help establish a Portland metropolitan wide traffic and transit data set, using Bluemac’s APIs offered by Site Services they were able to deliver data to Portland State University’s PORTAL (Portland Oregon Regional Transportation Archive Listing) system using a privacy scheme that addresses citizen concerns.
As the Washington County’s population continues to grow, the Traffic Engineering Department will further use their expertise to effectively manage the transportation infrastructure for the benefit of their constituents, with one tool available to them the Bluemac system.