How Much Distance to Spot the Pedestrian?

Owl Autonomous Imaging is dedicated to reducing pedestrian fatalities.  One of the most important things we can do is to ensure automobiles have adequate time to stop, when a pedestrian or other vulnerable road user crosses their travel path.  

Of course, this is complicated and involves many moving parts – a human driver that might be checking their cell phone, unpredictable nature of pets and children and the challenges of spotting a pedestrian early enough to take action.  

Stopping before a collision requires adequate time for deceleration after an object is detected. Charts of stopping distances have been developed to provide guidelines. This one from Australia [3] is representative:

Reaction times are just one factor in determining how much visible distance is necessary to stop a vehicle before it impacts with a pedestrian. Notably, up to 70km/h – most of the braking distance – is generated by human reaction time, on the order of 750ms.  Therefore, the ability to save lives rests in the ability to transfer braking reaction to autonomous emergency braking systems. 

The total braking distance includes both the distance traveled while the driver is recognizing the hazard and the distance traveled during brake application. While the typical detection time for an electronic system is generally faster than the human reaction time, the traditional values will be used here for conservatism. The conclusions to be drawn from the chart are that pedestrian distances up to at least 150 meters should be measurable on the highway while 70 meters should be sufficient on city streets. 

Automotive engineers seeking to improve visibility and reaction times must take all of these factors into consideration.  This equation above, just being one of many requirements to consider.  

Download our latest white paper – Requirements for Effective Pedestrian Imaging for the full explanation and best-practices for all the challenges and requirements here: 

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