by Lauren Martinelli
The Project
In the summer of 2025, I had the opportunity, through the CapaCITY/É team grant funding, to collaborate with transportation specialists at the City of Guelph to assess sites of radar speed boards and traffic calming interventions. This project was under Objective 2, which addresses intervention impacts on vehicle speeds. The project was exploratory and aimed to describe the built environment and surroundings of sites where radar speed boards and traffic calming measures were implemented in the City of Guelph and the effects on speed.
The City of Guelph and Vision Zero
The City of Guelph was invested in this project, as they have committed to achieving the Vision Zero goal of preventing all collision-related severe injuries and deaths, through strategies like designing safer roads and reducing vehicle speeds (City of Guelph, 2025). Calming vehicle speeds is an important public health mission, as high speeds increase the likelihood of collisions and worsen injury severity and mortality from collisions (NACTO, 2020; Wu et al., 2020). As part of its Vision Zero Action Plan, the City of Guelph has used traffic calming and other safety measures, including radar speed boards, to respond to traffic concerns.
Figure 1. Radar speed board. Photo: Dwernertl, 2007.
Figure 2. Speed cushion. Photo: Drdul, n.d.
What We Did
We used location data from the City of Guelph, as well as satellite imagery and Google Street View to characterize radar speed board and traffic calming measure sites. We mapped characteristics of the environment, including speed limits, number of lanes, roadway widths, school zones, street segment length, curvature, and on-street parking. Speed measurement data, including before and after installation average daily speeds, 85th percentile speeds, and percent of vehicles travelling above the posted speed limit were obtained from City of Guelph datasets.
We described all radar speed board sites (49) that had been active in the City of Guelph as of June 2025, and all traffic calming sites (speed humps, speed cushions, and traffic calming curbs) (70) that had been implemented since 1998. We were able to examine pre-post effectiveness for 9 radar speed board locations and 19 traffic calming measure locations, based on availability of before and after installation speed data. We tested for significant associations between site characteristics and percent change in average daily speeds.
Figure 3a. Example of satellite imagery of road curvature. Photo: GoogleMaps.
Figure 3b Satellite imagery street segment lengths. Photo: GoogleMaps.
What We Found
The main findings of this project were the following:
- Radar speed boards
- Following installation, locations had significantly lower average daily speeds, 85th percentile speeds, and a lower proportion of vehicles travelling above the speed limit.
- Most effective sites were in school zones, in 30km/h speed zones, and with short street segment lengths.
- Speed cushions
- Greater speed reductions in 50 km/h speed zones, as compared to 30 km/h zones.
- Most effective sites had on-street parking, at least 2 radar boards nearby, and at least 3 other traffic calming devices nearby.
How Our Findings Will Be Used
Our report to the City of Guelph recommended that radar speed boards be implemented, strategically, in areas with pre-existing low-speed features, including other traffic calming measures, to optimize effectiveness. In areas with higher speed environments, like those with more than two lanes or with 50km/h limits, speed cushions were recommended to be used, as opposed to radar speed boards, to optimize speed reductions. It was also suggested that pairing multiple measures with a speed cushion may be more effective than any one measure on its own.
This project will help to inform future implementation of traffic calming measures and radar speed boards in the City of Guelph. These findings will help the City of Guelph prioritize new locations for these initiatives where they are likely to have the most impact for reducing vehicle speeds, therefore increasing the safety of Guelph residents. A future study is planned based on this work to examine the optimal built environment surrounding automated speed enforcement cameras to facilitate speed reduction.
Figure 4. Traffic calming curb and speed hump in Guelph. Photo: Vivian, 2022
Lauren Martinelli is a Master of Occupational and Public Health student at Toronto Metropolitan University, studying child and youth active school transportation in the City of Guelph. They worked as a research student for CapaCITY/É in collaboration with the City of Guelph’s transportation team over the summer of 2025. They are passionate about supporting sustainable transportation and promoting health equity through public health initiatives.
References
CapaCITY/E. (2026). Objective 2 – Examine. https://capacity-capacite.ca/examine/
Drdul, R. (n.d.) Speed hump (likely located in British Columbia, Canada) [Photograph]. Traffic Calming Flickr Photoset. https://commons.wikimedia.org/wiki/File:Speed_hump_1.jpg
Dwernertl. (8 August 2007). Standard radar sign [Photograph]. English Wikipedia. https://commons.wikimedia.org/wiki/File:Standard_radar_sign.jpg
NACTO. (2020). City limits: Setting safe speed limits on urban streets. National association of city transportation officials. https://nacto.org/wp-content/uploads/NACTO_CityLimits_Spreads.pdf.
Vivian, R. (2022). [Calming curbs on Forest Street] [Photograph]. GuelphToday. https://www.guelphtoday.com/local-news/calming-curbs-have-come-to-guelph-to-slow- down-drivers-5582682
Wu, M., El-Basyouny, K., & Kwon, T. J. (2020). Before-and-after empirical Bayes evaluation of citywide installation of driver feedback signs. Transportation Research Record, 2674(4), 419-427.