In view of my recent encounter with a camera van and the fact that the police prefer to refer to them as Safety Cameras instead of Speed Cameras, I thought I'd crunch a few numbers to see how safe keeping to the speed limit actually is.
Sadly, I was too lazy to resolve a formula myself, so I turned to google and the help of Dr. Math.
http://mathforum.org/library/drmath/view/56330.html
Two examples both assuming that:
1) the car being overtaken is doing a constant 55 mph
2) it takes about 12 car lengths to get past the car and the car is 15 feet long, giving a distance to be covered of 180 feet (d)
3) the passing vehicle is also doing a constant speed (v2)
The formula is required to calculate D, distance needed to pass
D = d x v2/(v2-v1)
Example 1
The passing vehicle (v2) is doing 60 mph
the overtaken vehicle (v1) is doing 55mph
D = 180 x 60(60 - 55) = 2160 feet (0.4 mile)
from this we work out how long it would take to pass since 60 mph = 88 ft/sec
2160/88 = 24.5 secs.
Example 2 (my case)
The passing vehicle v2 is doing 70 mph
the overtaken vehicle is doing 55 mph
D = 180 x 70 (70-55) = 840 feet (0.16 mile)
and the time? 70 mph = 102.6 ft/sec
840/102.6 = 8.2 secs
So:
at 60 mph it requires 2160 ft and 24.5 secs
at 70 mph it requires 840 ft and 8.2 secs
I could imagine going to court with this, watching the court's eyes glaze over and then told to pay the fine anyway
