Thursday, Sep 14, 2006 at 10:09
>Caused by the normal muli-path phasing effects,as both
>vehicles are in the field of view at same time.
With a 100m gap?! And if that were the case it would make these speed check points all but useless except at 3am in the morning with only one car on the road and we would be hearing dozens of reports of how inaccurate they are? I’ve gone through them many times with other traffic (closer than 100m too) and they have provided an accurate reading for all.
>Doesn't happen anywhere near the same for roadside camera's as
>apart from better processing of more expensive units, they use a
>very tightly focussed beam angled at 22.5 degree down road.
So you're saying that dozens (hundreds?) of mobile speed cameras which are placed by hand at the roadside have better directional antenna and capabilities than half a dozen specifically designed fixed measurement instruments where the environment is known and cost is much less of an issue. This is a bit like saying my kitchen scales are more accurate than a weighbridge.
>Here is required a gap between vehicles (as seen by radar) to in effect
>reset reference value to zero before a valid reading can be logged on
>next car.
And a 100m gap is insufficient to do that? No other traffic, in sight, on the road at all either behind or in front.
It also begs the question that if roadside units rely upon the local environment to obtain their baseline how do they cope with such an uncontrolled situation? The rotating wheel of a child’s cycle, for example, may give them a false zero – how would they know?
Mike Harding
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