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Detect stop sign compliance - FLOW Insights How-To Series
Detect stop sign compliance - FLOW Insights How-To Series

Learn how to detect stop sign compliance and violations and in turn improve road safety.

DataFromSky avatar
Written by DataFromSky
Updated over a week ago

Is it okay to not stop at stop signs? No, it is not! “Nearly 700000 police-reported motor vehicle crashes occur annually at stop signs, and approximately one-third of these crashes involve injuries." (Retting, Weinstein and Solomon, 2013) In our article, you will learn how to design a smart camera and improve road safety at stop signs.

We all know that sometimes the traffic sign placement is not optimal but stop signs on narrow city street corners make perfect sense and improve safety by a lot. Unfortunately, enforcing drivers’ compliance can be complicated but FLOW is here to help. Smart traffic cameras running FLOW can provide actionable real-time information and evidence to help reduce this unwanted behavior.

This article will teach you how to use FLOW to set up stop detection at stop signs.

If you are new to FLOW - read this article or watch our webinar to get familiar with the basics. Links to more FLOW specific guides can be found below.

What will you learn from this article?

  1. How to set up the detection of vehicles running a stop sign.

  2. How to use a stationary duration filter.

  3. How to create widgets for monitoring stop sign compliance.


First, we drag and drop a category filter to the canvas. We double click it to open its menu and we tick boxes to select the following categories: car, light, heavy, bus, and motorcycle as shown in the picture below. We do this because we want to detect only motorized vehicles.

Next, we create a gate by drawing a line in the footage with the Create zones/gate tool found in the top left corner. In this particular scenario, some cars coming from the junction are cutting their turns and using the opposite lane which would add invalid counts to our measuring.

Then we need to create a zone where cars should stop. We create the zone by drawing until we connect the lines to form at least 3 sided object. We always select a slightly larger area to account for vehicles being outside their lanes. After creating the zone and gate we drag them over to the canvas and name the gate "Direction Gate" and the zone "Stop Detection Zone".

When we double-click the gate in the canvas we select a single direction, in this case, the direction with the white arrow which continues into the stop detection zone.

The order of connecting the spatial filters is important. We put the movement first to filter out unwanted traffic that was mentioned earlier. We connect the movement filter to the category filter. Below movement, we connect the stop detection zone. Now we can add stationary duration motion filters in the canvas and connect them both to the stop detection zone. Drag and drop 2 stationary duration motion filters onto the canvas. First, we create a filter called “No Stop”. we select “value”, then “less” and then type 1 in the box. We name the second filter “Proper Stop” we select “value”, then “greater” and then type 1 in the box. This filter will show us the number of vehicles that stopped for more than 1 second and therefore complied with the stop sign.


To help us monitor the situation we will add value widgets to both of the stationary duration filters. We click on the val (value) next to the “OK Stop” filter and at the bottom of the menu we click “add a new color” and select green. We do the same for the “NO Stop” filter but we select red instead. To see the current situation when checking values in the dashboard, we can add the trajectory view widget to the category property filter on the top of our canvas which will show the video feed of the current situation with trajectories.


In this guide, you have learned how to detect both proper stops and occurrences of drivers running a stop sign. You have also learned how to filter out vehicles coming from the wrong direction with the help of a gate direction setting. What can you do with this data? For example, you can put a LED display on the junction to show drivers in real-time if they stopped and for how long. To reinforce positive behavior you can show the drivers a smiley face and a thank you when they stop. If they do not stop, show them a big warning sign instead.


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Thank you for your interest! Have a great day!

Let the traffic flow - with FLOW!

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