Citizens use sensor data to adjust traffic measures
You tackle the following challenges:
General
The city of Sint-Niklaas is going to renew the public space in the residential Vogelkeswijk with garden streets. Garden streets are streets that are transformed to bring more greenery and water into the urban environment. This is done by, for example, depaving part of the road, providing planting areas, planting trees and providing wadis. The goal is to make the living environment more beautiful, more pleasant and more sustainable, which also contributes to more biodiversity and better water management.
Prior to the construction of garden streets, the city of Sint-Niklaas tested new traffic measures to make the school environment and the residential streets of the Vogelkeswijk safer. The European citizen science project COMPAIR, which aims to help improve air quality in urban areas, supports the city of Sint-Niklaas and its residents in measuring the effects of these measures. Is there less rat-running traffic thanks to the new traffic measures? Are the speed-reducing measures effective? Has the air quality improved?
The test setup
To prevent rat-running traffic, three streets in the Vogelkeswijk were set up as one-way streets from 10 June to 15 October 2024, with traffic from Zwaluwenlaan and Vinkenlaan merging into Nachtegalenlaan. To better enforce the 30 km/h zone, the city installed several speed bumps.
Ten residents have been measuring traffic in and around the Vogelkeswijk since March 4, using a smart traffic sensor (Telraam), which can distinguish and count pedestrians, cyclists, cars and heavy traffic. Air quality sensors with solar panels have been attached to four (lighting) poles, which measured nitrogen dioxide (NO 2 ) for 3 months before and 3 months during the test setup.
Participation
The results were discussed with residents of the district during publicly accessible data cafés.
A data café is an initiative that brings people together to learn about and work with open data. The idea is to create an informal and accessible environment where participants can network, exchange ideas and collaborate on data-related projects. Often workshops, presentations and hands-on sessions are organized to increase the skills and knowledge of the participants.
The data cafés in Sint-Niklaas were organised by the Flemish partners from the COMPAIR consortium (Flemish Environment Agency, Telraam and Digital Flanders) who, as a neutral actor, assisted the City of Sint-Niklaas and its residents.
Analysis & Discussion
Traffic counts
We compare the measurement data 1 month before (from 6/5/2024 to 6/6/2024) and 1 month during (from 9/9/2024 to 9/10/2024) the test setup. Overall, we count 33% fewer cars in the district but also 25% fewer cars in the neighborhood, due to road works in the area (Sint-Gillis-Waas). Given that the decrease is much stronger in the Vogelkeswijk than in the neighborhood, we can attribute this to the new traffic measures. The one-way streets (and speed bumps) appear to be effective in combating the rat-running traffic at the light-controlled intersection of Heistraat/Lepelhoekstraat.
In Zwaluwenstraat, car traffic has decreased by 75% (from an average of 251.94 cars to 67.56 per day) and in Vinkenlaan, car traffic has halved (from an average of 487.00 to 219.41 cars per day). There are now even more cyclists than cars in Vinkenlaan, which provides access to the primary school. Car traffic in Vinkenlaan, on the other hand, has increased by 40% (from an average of 218.16 to 302.47 cars per day).
The tested measures seem effective in keeping unnecessary traffic out of residential streets, without negative impact on the capacity of the main axes. There is a limited internal movement of traffic within the district to Nachtegalenlaan.
Residents of Zwaluwenlaan and Vinkenlaan are very satisfied with the decrease in car traffic and the safer situation for active road users. Residents of Nachtegalenlaan are requesting, via a petition with traffic data, an adjustment of the traffic plans so that the remaining traffic is better distributed over the four streets of the Vogelkeswijk. The proposal of the residents to introduce a cut in Vinkenlaan (at the T-junction with Nachtegalenlaan) is being investigated by the city services.
Air quality measurements
Although the impact of the traffic measures was relatively large, the streets in question are locations with low absolute figures when it comes to traffic density. We therefore expect that the differences in nitrogen dioxide concentrations in this district will also be small overall.
The measurements confirm this: although the general change in the district between pre- and post-measurement is greater than that for our reference location in Borgerhout (where no change occurred), the evolutions of the sensors are not mutually reconcilable with the conclusions that affect the counting frame sensors. This indicates that other effects (local meteorological effects, sensor drift, calibration differences, ...) had a greater impact than the district mobility plans on the total distribution of nitrogen dioxide measurements.
A suggestive difference that does emerge in the analysis is the absence of a second peak in the distribution plot in the post-measurement compared to the pre-measurement for the streets where a positive impact on traffic density was found. This second peak, which indicates a higher concentration level that was frequently measured (eg via a peak in traffic) seems to be suppressed in the post-measurement. This effect could possibly be an echo of the mobility changes. However, the conclusion seems to be that the impact of the district mobility plan was too small in absolute terms to detect with an air quality sensor.
Conclusion and next steps
The COMPAIR solutions (in this case traffic counts, dashboards and data cafés) have contributed to improving the dialogue between city services and citizens. Both city and citizens have been able to substantiate various assumptions with data. The final traffic measures are information-based, take into account proposals from citizens and seem to be widely supported.
The Telraam sensors were donated to the participants. And the city of Sint-Niklaas invited the citizen scientists to count traffic up to and including the construction of the garden streets.
