IMSA Journal | Nov/Dec 2014
By Steven J. Kimble, P.E., Regional System Consultant, Sensys Networks, Inc.
The transportation industry is ex- periencing unprecedented focus on addressing bicycle usage as a grow- ing means of transportation and a critical part of Complete Streets ini- tiatives across the country. With ever-rising gas prices, congested roadways, and increased political and economic emphasis on green technologies and transportation, the demand and public visibility of bi- cycling will only grow. A key out- come of this increased focus is the need to service bicyclists at signal- ized intersections, as well as the need to know how many bicyclists are using infrastructure invest- ments, how is that usage trending, and how to best deploy the re- sources available for this growing demographic.
One of the fundamental chal- lenges faced by transportation agen- cies and professionals is detecting and serving these bicyclists at signalized intersections without sig- nificantly impacting the already congested vehicular traffic flow. In addition, engineers and planners struggle to accurately measure bicy- cle traffic. Traditional vehicle count- ing methodologies, such as loops or tube counts, are not viable due to maintenance and installation chal- lenges. Unlike vehicles, weather and time-of-year create significant variability on bicycle traffic.
Single Solution for Safety and Planning
Bicycles present their own unique set of detection challenges. They are relatively small in size and profile, and composed of few ferromagnetic components, making their detection by traditional means difficult. How- ever, in using the latest technologies in both wide-band radar and low- power wireless transmission, solu- tions have emerged to deliver promising changes to the way bicycles fit into the transportation land- scape. New radar and wireless tech- nologies are now embedded into a small battery-powered in-ground sensor that can not only detect bicy- cles of all kinds (including carbon- fiber bicycles with little or no metals) but also differentiate be- tween a bicycle and a motorized vehicle. The ultra-low power con- sumption allows the high-accuracy sensor to operate on battery for an expected 8-year period.
Figure 1: Wireless sensor
These wireless sensors detect bi- cycles by transmitting a very low power, high frequency RF pulse, which bounces off the target (bicy- cles and/or vehicles) and measure the reflected energy profile of the RF pulse from the object. Using on-board processing and logic, the sen- sors analyze this profile to deter- mine not only if an object is present, but the approximate size of the ob- ject to determine if it is a bicycle or a larger vehicle. The ability to detect and differentiate bicycles enables traffic engineers to effectively time traffic signals for motorized vehicles and bicycles, simultaneously in- creasing safety and intersection efficiency. For example, greater min- imum green light time can be allot- ted when a bicycle is present to allow bicyclists to safely cross an in- tersection.
Bicycle detection events that occur at the in-pavement sensor are transmitted wirelessly to a pole- mounted radio wired into the traffic controller cabinet. Detection events can be passed to contact closure channels, separated by bicycle or vehicle detection, as well as passed to data collection and management software over IP networks.
For bicycle count data collection, a server collects and stores every bi- cycle detection event, allowing the end-user to analyze bicycle flow Wireless count with greater detail than ever before. Bicycle detections can be reported in time-aggregated intervals from 1 minute to hourly increments (Fig- ures 2 and 3). The server also col- lects sensor and wireless radio diagnostics (e.g., wireless signal strength and battery status) and can proactively alert users if mainte- nance is required.
Figure 2: Tabular report showing binned bicycle volume, occupancy, and speed data at 15 minute increments
Figure 3: Graphical report showing binned bicycle volume data at 15 minute increments.
What’s more, these new bicycle detection advances can be delivered utilizing the same wireless commu- nication platform used to actuate signals for vehicular traffic, collect traffic data, and calculate vehicular travel time. The addition of bicycle detection to this single platform allows for increased multi-modal analytical capability enabling city planners to improve safety conditions and accessibility accordingly (Figure 4).
Figure 4: Graphical report showing binned vehicle and bicycle volume data per lane.
Deployment
The wireless radar bicycle detec- tion solution is suitable for traffic signal actuation in both shared use and/or dedicated bicycle lanes. For counts and data collection the solu- tion is best deployed in dedicated bicycle lanes. The sensors’ settings can be tuned to optimize actuation, differentiation, or counting per- formance.
For bicycle traffic signal actua- tion, the sensor is typically installed six inches in front of the stop bar in the middle of the lane. The detec- tion radar is aimed away from the stop bar toward oncoming traffic (Figure 5). This configuration is used to both detect bicycles and ve- hicles, as well as to differentiate be- tween the two.
Figure 5: Wireless sensor deployed in a shared lane facing oncoming traffic.
For count installations, the wire- less bicycle sensor is deployed on the edge of a dedicated bicycle lane in an area with free flow bicycle traffic and aimed at a 45 degree angle across the bicycle lane and to- wards oncoming traffic (Figure 6).
Figure 6: Wireless sensor deployed in a dedicated bicycle lane located on or past the limit line.
is kept relatively level with roadway surface and no more than 1/4″ (.6 cm) from the top of the pavement sur- face. The cored hole with the sensor in it is covered with a quick-drying epoxy. Typical installation is less than 10 minutes per sensor – allowing the road to be re- opened with significantly less impact than loop detec- tors. The result is a robust and dependable bicycle detection solution with minimal impact to the roadway surface (Figure 7).
Figure 7: Installed wireless bicycle detection sensor.
Conclusion
Bicycle detection is rapidly becoming a new require- ment for many agencies, and effective solutions are growing in urgency for those who need to accurately and safely manage bicyclists on the roadways. With in- creased focus from FHWA and various political ele- ments, the demand for servicing bicycles with minimal impact to other modes of travel will only increase. Using the latest low-power wireless communications and accurate wide-band radar enables users to detect all bicycle types, gather data continuously, and provide a wealth of information not previously possible to meet civic planning needs.
