Smart traffic monitoring in Amsterdam: How fiber optic sensing contributes to future-proof infrastructure
The pressure on Amsterdam's bridges and quay walls is great. Not only due to age, but especially due to increasing traffic loads – streets built for horse & carriage are now being used by 30 ton trucks. Until now, the municipality worked with cameras that register the type of vehicle to estimate the weight. But a camera does not see whether a truck is empty or full. A wrong weight estimate can lead to either premature and unnecessary maintenance or delayed action that risks causing damage.
This is why the Municipality of Amsterdam is working with PhotonFirst on a much more accurate solution: a Weigh-in-Motion (WIM) system based on optical fiber technology.
From visual to physical measurement
Instead of just looking at vehicles, we are now really measuring what they weigh. Integrated into the asphalt of the Droogbak – an access road to the city center near Amsterdam Central Station - are optical sensors that measure the deformation of the road surface as a vehicle passes. These tiny deformations are converted into exact weight information per axle and wheel. All in real time, without hindering traffic.
What exactly is installed?
The system consists of three sensors (so called sensor beams), each with 40 Fiber Bragg Gratings (FBGs) - optical reflectors in a fiber that respond to deformation. The sensors are positioned so that they mainly detect weight, and are not disturbed by braking or acceleration, for example. Everything is connected to a specially designed measuring cabinet with interrogators, a mini-PC and storage capacity. The system is installed flush into the asphalt, making it invisible and maintenance-free.
All this was prepared and executed in cooperation with Technobis.
Installation overnight
The sensors were placed in grooves in the asphalt, connected, and covered with filler material specifically designed for long-lasting road repairs. Within one night, the system was fully integrated - without the need for lengthy road closures.
Why fiber optic sensing?
Fiber optic sensing is extremely sensitive, interference-free and needs low maintenance. The measuring principle is insensitive to electromagnetic interference, works in wet and dusty conditions and is ideal for long-term, accurate monitoring in public spaces. A major advantage is also that the system can run autonomously for years, while the data remains remotely available for analysis.
For the municipality, this means:
- Better decisions: No more estimates, but hard data on axle load and vehicle weight.
- More focused maintenance: No unnecessary costs for premature maintenance, no risk of damage due to late intervention.
- Substantiation for policy: With accurate data, new rules or measures can be substantiated.
- Preparation for enforcement: In combination with cameras, the system is suitable for automatic enforcement on overloading in the future.
- Ready for the future: Smart infrastructure
And what does PhotonFirst do?