Re: Scenario (Was: Are radar\laser detectors legal to us in the UK?)


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"Karl Foley" <karl@xxxxxxxxxxxxxxxxxxx> wrote in message
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I decided to start a new thread because the old one seems to have
generated a bit of name calling.

I thought the scenario that prompted the question would be of
interest.

I live in a small town on the east coast called Felixstowe. There is
one main route in and out of the town which is the A14.

Going into Felixstowe (about 4 miles out), there is a long left bend,
followed by a straight, followed by a long right bend. The A14 is
dual
carrigeway along it's entire length.

I was on the long left bend approaching the straight in the inside
lane
doing 70 MPH. There were about 7 cars driving at approximately 60 MPH
in front of me. Upon reaching these cars I was now on the staight,
and
having checked my mirrors I could see no one approaching from the
rear
so I signalled and changed lane to pass.

I had passed approximately 2 cars when I observered another car
rapidly
approaching from the rear. I am not an expert but due to the closing
speed I would expect the approaching car was doing in excess of 100
MPH.

I considered pulling in to the inside lane but there was not really
the
space to do so (the cars were bunched together) so I continued to the
overtaking manouvre at the same speed.

The approaching car then tailgated me, leaving no more than a few
feet
between our cars. We were then approaching the right hand bend so I
decided the safest option was to accelerate and increase the gap
between the tailgating car and mine, in order to expediate the
overtaking manouvre and to get out of the way of this maniac.

Did it not occur to you that as the car behind you had approached at a
speed you estimated at around 100mph, if you increased speed, he would
do so also? In other words, you would not have increased the gap
between you but rather have had him tailgating you at 85 mph rather
than at the legal 70 mph, which would have been even more dangerous? !


As I did so, I started to round the right hand bend, only to see a
police car on the opposite carrigeway. This car was parked in the
hashes on an entry sliproad onto the other carrigeway. The passenger
door was open, and what looked like a camera was behind the door
looking through the rolled down window.

I was doing an indicated 85 MPH when I saw the police car but decided
I
couldn't slam on my brakes as I would get rear ended by the following
car so I simply ceased the acceleration and hoped the police car was
monitoring the other carrigeway.

The 14 days for a NIP ends on this Friday so I just sit here with my
fingers crossed! (Of course, I can only get a NIP as my car is
properly
registered and I assume Tax\MOT and Insurance are all checked as part
of the process). If I had had a lasar\radar detector, I might have
known about the speed trap and taken another course of action. In
this
scenario, I would feel unfaily treated because, as a (generally) law
obiding motorist, I would be penalised, not the dangerous driver
behind
me.

Firstly, by the time a laser detector gives you a warning, the officer
operating the laser will already be reading your speed.

Simple law of physics - whatever beam is used must have a return path
to be measured by the sender.

A good analogy is the Japanese Kamikaze bombers, they soon worked out
they had twice the fuel range if they didn't have to make the return
trip.

I'm not convinced that that was the prime driver behind the Kamikazi

No one suggested it was - it seemed so obvious as to go without saying
their prime driver was to pack an aircraft with explosives and crash it
into an American carrier (move to a binaries and I can draw pictures for
you!) - the fact that not having to make the return trip doubling their
fuel range was obviously a bonus.

technique. I don't think the analogy is right either.

The analogy seems obvious enough to me the beam can only be transmitted
at a specified power (laser can burn the retina of the target/victim,
microwave radar can cause cataracts) and a Mitsubishi Zero can only so
far on the fuel it can carry - in both cases each can only travel a
certain distance. The Zero can hit a target twice as far away if it
doesn't need fuel reserve to make the return trip, and a speed gun beam
is detectable at twice the trapping distance because the beam to target
and back again can only cover half the distance that the straight one way
path of the beam from gun to a detector on the target still carries
enough energy to be detected.


My concern here was that the outgoing laser beam, being a pencil beam has,
for this purpose, a more or less unlimited range.


I'm guessing here but since a narrow beam of coherent light would be
difficult to arrange a sensor to be in exactly the right place to detect the
more or less randomly aimed beam, detection might rely on scatter from
particulates in the air - if this be the case detection might actually
become more difficult the closer you get to the gun.

As for the return beam, its scattered in all directions from the point it
hits the target - so only a tiny fraction of the total energy finds itself
going in the right direction to hit the detector on the gun.


.

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