Traffic Masking

February 2, 2008 at 10:10 pm 1 comment

Today, I want to formally introduce a concept that probably everybody is informally aware of.

It’s called traffic masking, and it’s a most useful concept when riding a bike. The embodiement of this concept in everyday traffic situations becomes a mechanism that allows a bicycle rider to flow through traffic more smoothly.

Let’s introduce some terminology first :

  • source zone : part of the road that you are currently on
  • target zone : part of the road that you are going to be on
  • conflict traffic : all traffic participants whose target zone overlaps your target zone

The general idea of traffic masking is that something, or someone, masks your target zone.
Masking in this case means that your target zone is explicitly or implicitly free from any conflict traffic. This allows you to transfer from source to target zone without fear of collision.

Below I’ll show some examples. The first two may be known to you, but the last one is somewhat more exotic.
The big rectangles are cars, the pencil-like shape is supposed to be a bicycle. Please click on the images for full size view.

First a very direct form of masking, one car is blocking another car. This kind of masking is hard masking, since the there is no way for the conflict traffic to reach your target zone. In other words : the blocked car cannot overrun the blocking car.


Next is a more indirect form. A pedestrian crosses the road and block the passage of a car. There is no hard barrier for the conflict traffic, so this is a soft form of masking. The car could run the pedestrian over, and still hit you.


The last example is perhaps not intuitively recognizable but it is a valid masking mechanism.
In this case, a slow moving car prohibits a faster moving vehicle from maintaining its speed. This results in a short window for the bicycle rider to slip behind the slow car without immediate collision danger. This is of course the softest form of masking since no objects are between your target zone and the conflict traffic.


So next time while riding a bike in traffic, try to recognize masked zones as soon as possible.

An advanced technique for smooth traffic flow is when you find your target zone to be unmasked and imminently invaded by conflict traffic, to substitute it for another zone, that is masked. This manoevre only pays off if it’s possible to re-route your path so that the time gained by switching zones, is not fully consumed by the time needed for the detour.


Entry filed under: Truly important stuff.

C++ quick trick : named constructors One of you has to go

1 Comment Add your own

  • 1. Peter  |  February 5, 2008 at 12:22 pm

    hmm, interesting, I never thought about it that way.


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