The Ranty Highwayman)
3 December 2016
“FILTERED PERMEABILITY” IS A TERM OFTEN USED BY PEOPLE TRYING TO DESCRIBE THE ACT OF PREVENTING PEOPLE FROM DRIVING THROUGH AN AREA, BUT IT IS A LITTLE MORE COMPLICATED WHEN WE NEED TO PROVIDE ACCESS.
At a basic level, “filtered permeability” utilises strategically placed “road closures”, or “modal filters”, to prevent people driving motor vehicles through (normally) a residential area in preference to a main road. In this case, the road is only “closed” to people driving through to gain an advantage, people who live in an area and wish to drive in and out can still do so. Deliveries can still be made and refuse collected. People can walk and cycle through with no impediment too.
The image above gives a rough idea of how we can use some modal filters to keep access into an area for motors, but prevent it’s use as a through route.
A modal filter can take all sorts of forms including gates, bollards, planters, kerbs, concrete blocks and so on. So let’s look at a few real examples;
I do not speak for the emergency services by any means, but in my own experience, they would generally treat a modal filter as a location to avoid, preferring to use the same route which drivers would normally take. Increasingly, those driving emergency vehicles may not be working a local “patch” and so satellite navigation is increasingly being used and in that case, the modal filters will show as closures.
The ability to open a filter is more generally helpful some time into an incident and the vast majority of the time will be something the fire brigade will do. This is generally because the fire brigade will carry keys to the gate or bollard (normally a universal key, but local agreements operate) and the police and ambulance don’t. If there is a fire or large incident with lots of “kit” on the scene, then opening a filter gives another option for moving things and people in and out of the area.