Stopped for speeding?

Tony Raven said:

Nobody Here wrote on 11/04/2007 16:27 +0100:

Quoted message said:

Quoted message said:

>From memory, I would have to look it up to be precise, and it would
depend on the type of gun being used, but the LTI 2020 has a beam of
about 3500meters and a 1m divergence at 1000m. At normal distances
this equates to about 4.5 to 8.0 cm of target area.

Hmmm, I wonder what frequency those radars operate on. By my calculations
using my rather rusty antenna theory to get that divergence at 3GHz you'd
need a 130m dish antenna. That's a divergence of about 0.06 degrees
which is pretty tight. For example, the deep space network 64m antenna
at Coldstone in the US has a beam width of 0.04 degrees at 8.4GHz.

It will be a laser based one which needs a far smaller aperture to
achieve that divergence figure.

Oh, of course, I didn't think of that! Yes, a mm or two would be more than
adequate.

--
Nobby Anderson

Marz said:

Dylan Smith said:

So on my ride into work today, I passed a policeman who was running a
radar speed trap. He was pointing the handheld radar gun at me (there
were no cars behind me, so he was definitely pointing it at me).
Firstly, it was wishful thinking that I'd be anywhere near the 30mph
speed limit - but I was surprised I'd present enough of a radar
reflection for his speed gun to work.

Have the police ever pulled a cyclist over in a radar trap? Have
cyclists ever set off a GATSO?

--
Yes, the Reply-To email address is valid.
Oolite-Linux: an Elite tribute:http://oolite-linux.berlios.de

Pulled over once in Lanner about 20 years ago. Coming over the top
from Redruth there's a nice drop down into the village of Lanner and
on this occasion a great tail wind. Reaching about 44 in a 30 zone.
The cop gave me a right telling off, but didn't bother to give me a
ticket as he realised I had no i.d. on me.

Or perhaps the police officer had a better idea of the law.
There is no offence of speeding on a bicycle on the road in the UK (a couple
of parks have specific by laws). All the speeding laws refer to motor
vehicles.

You could have been charged with "furious riding" or something similar. But
its years since anyone was charged with that.

Quoted message said:

I used to get odd looks from police on the A30 when I dropped into the
slip streams of passing trucks. It was quite easy to maintain an
amazing speed, sometimes around 60, but I guess I wasn't speeding.

Correct, you'd not be speeding at 100mph. The trucks and cars might be
speeding.

- Nigel

--
Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/

Nigel Cliffe wrote on 11/04/2007 18:53 +0100:

Quoted message said:

You could have been charged with "furious riding" or something similar. But
its years since anyone was charged with that.

1997 to be precise. Tony Adams in Cambridge under Section 28 of the
Town Police Clauses Act of 1847. He was fined £120 IIRC:

28.
Every person who in any street, to the obstruction, annoyance, or danger
of the residents or passengers, commits any of the following offences,
shall be liable to a penalty not exceeding [level 3 on the standard
scale] for each offence, or, in the discretion of the justice before
whom he is convicted, may be committed to prison, there to remain for a
period not exceeding fourteen days,...

....Every person who rides or drives furiously any horse or carriage, or
drives furiously any cattle:

--
Tony

"The most savage controversies are those about matters as to which there
is no good evidence either way."
- Bertrand Russell

In article said:

Nobody Here wrote on 11/04/2007 16:27 +0100:

Quoted message said:

Quoted message said:

From memory, I would have to look it up to be precise, and it would
depend on the type of gun being used, but the LTI 2020 has a beam of
about 3500meters and a 1m divergence at 1000m. At normal distances
this equates to about 4.5 to 8.0 cm of target area.

Hmmm, I wonder what frequency those radars operate on. By my calculations
using my rather rusty antenna theory to get that divergence at 3GHz you'd
need a 130m dish antenna.

It will be a laser based one which needs a far smaller aperture to
achieve that divergence figure.

Google confirms that, but suggests a lower range.
http://www.lasertech.com/ulproduct.html
http://www.lasertech.com/Speed_Enforcement/Speed/Handheld/UL_Series.htm

Alan Braggins wrote on 11/04/2007 19:39 +0100:

Quoted message said:

In article said:

Nobody Here wrote on 11/04/2007 16:27 +0100:

Quoted message said:

> From memory, I would have to look it up to be precise, and it would
> depend on the type of gun being used, but the LTI 2020 has a beam of
> about 3500meters and a 1m divergence at 1000m. At normal distances
> this equates to about 4.5 to 8.0 cm of target area.
Hmmm, I wonder what frequency those radars operate on. By my calculations
using my rather rusty antenna theory to get that divergence at 3GHz you'd
need a 130m dish antenna.

It will be a laser based one which needs a far smaller aperture to
achieve that divergence figure.

Google confirms that, but suggests a lower range.
http://www.lasertech.com/ulproduct.html
http://www.lasertech.com/Speed_Enforcement/Speed/Handheld/UL_Series.htm

There seems to be two in your second link that go out to 1km

--
Tony

"The most savage controversies are those about matters as to which there
is no good evidence either way."
- Bertrand Russell

Chris Eilbeck submitted this idea :

Quoted message said:

Simon D said:

[email hidden] formulated on Wednesday :

Quoted message said:

On 11 Apr, 10:33, Dylan Smith <[email hidden]> wrote:
> Firstly, it was wishful thinking that I'd be anywhere near the 30mph
> speed limit - but I was surprised I'd present enough of a radar
> reflection for his speed gun to work.
> Have the police ever pulled a cyclist over in a radar trap? Have
> cyclists ever set off a GATSO?

I wonder how much surface area these guns need to get a reflection -

No idea.

Quoted message said:

say you're going at 20mph, the top of your tyres are moving forwards
at 40mph. Another argument against big knobbly bits on your tyres? ;o)

Yes, but they don't detect rotation speed; they detect the movement of
an object relative to the position of the gun operator, surely?

There are different devices on the market. Some work by detecting the
doppler shift in the returned signal, some work my measuring the
differential position and hence speed of the object they're pointed
at. There have been occasions where the police have tried to do
people for twice the speed they were actually doing because of the
radar return from the top of an advancing wheel being stronger than
that from the main bike body and rider.

I stand corrected - thanks.

--
Simon

"Tony Raven" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Alan Holmes wrote on 11/04/2007 18:33 +0100:

Quoted message said:

But they still need to produce the 'evidence', which you are entitled to
see before admiting the 'offence'!

You have no need to admit anything about the offence until you are asked
to enter your plea in Court.

You have to make a plea at the time you get a NIP!

Quoted message said:

--
Tony

"The most savage controversies are those about matters as to which there
is no good evidence either way."
- Bertrand Russell

Quoted message said:

Dylan Smith said:

Firstly, it was wishful thinking that I'd be anywhere near the 30mph
speed limit - but I was surprised I'd present enough of a radar
reflection for his speed gun to work.

Have the police ever pulled a cyclist over in a radar trap? Have
cyclists ever set off a GATSO?

I wonder how much surface area these guns need to get a reflection

Depends partly on which Swerling case provides the best approximation
for a cyclist.

Quoted message said:

Chris Eilbeck said:

There have been occasions where the police have tried to do
people for twice the speed they were actually doing because of the
radar return from the top of an advancing wheel being stronger than
that from the main bike body and rider.

Really? Would that be in the Royal Parks, or a misguided plod?

I would doubt very much that you could get a bigger return from a tyre
than from a whole MOTORbike.

Quoted message said:

Quoted message said:

Dylan Smith said:

Firstly, it was wishful thinking that I'd be anywhere near the 30mph
speed limit - but I was surprised I'd present enough of a radar
reflection for his speed gun to work.
Have the police ever pulled a cyclist over in a radar trap? Have
cyclists ever set off a GATSO?

I wonder how much surface area these guns need to get a reflection -
say you're going at 20mph, the top of your tyres are moving forwards
at 40mph. Another argument against big knobbly bits on your tyres? ;o)

Quoted message said:

From memory, I would have to look it up to be precise, and it would

depend on the type of gun being used, but the LTI 2020 has a beam of
about 3500meters and a 1m divergence at 1000m. At normal distances
this equates to about 4.5 to 8.0 cm of target area.

Frequency? Antenna size? How are you measuring the beam?

Tony Raven said:

Nobody Here wrote on 11/04/2007 16:27 +0100:

Quoted message said:

Quoted message said:

>From memory, I would have to look it up to be precise, and it would
depend on the type of gun being used, but the LTI 2020 has a beam of
about 3500meters and a 1m divergence at 1000m. At normal distances
this equates to about 4.5 to 8.0 cm of target area.

Hmmm, I wonder what frequency those radars operate on. By my
calculations
using my rather rusty antenna theory to get that divergence at 3GHz you'd
need a 130m dish antenna. That's a divergence of about 0.06 degrees
which is pretty tight. For example, the deep space network 64m antenna
at Coldstone in the US has a beam width of 0.04 degrees at 8.4GHz.

It will be a laser based one which needs a far smaller aperture to
achieve that divergence figure.

Owing to its higher frequency & shorter wavelength. Antenna physics
still applies.

Al C-F wrote on 12/04/2007 11:48 +0100:

Quoted message said:

Tony Raven said:

Nobody Here wrote on 11/04/2007 16:27 +0100:

Quoted message said:

>
> >From memory, I would have to look it up to be precise, and it would
> depend on the type of gun being used, but the LTI 2020 has a beam of
> about 3500meters and a 1m divergence at 1000m. At normal distances
> this equates to about 4.5 to 8.0 cm of target area.

Hmmm, I wonder what frequency those radars operate on. By my
calculations
using my rather rusty antenna theory to get that divergence at 3GHz
you'd
need a 130m dish antenna. That's a divergence of about 0.06 degrees
which is pretty tight. For example, the deep space network 64m antenna
at Coldstone in the US has a beam width of 0.04 degrees at 8.4GHz.

It will be a laser based one which needs a far smaller aperture to
achieve that divergence figure.

Owing to its higher frequency & shorter wavelength. Antenna physics
still applies.

Yep, try 1.22lamda/D for a wavelength of around 1um and you will find
that for a 1mm aperture beam at the measuring device you will get a 1.22
meter patch at 1000m as Noboby Here suggested above.

Nice to know that physics still works.

--
Tony

"The most savage controversies are those about matters as to which there
is no good evidence either way."
- Bertrand Russell

In article said:

Alan Braggins wrote on 11/04/2007 19:39 +0100:

Quoted message said:

In article said:

Nobody Here wrote on 11/04/2007 16:27 +0100:
>> From memory, I would have to look it up to be precise, and it would
>> depend on the type of gun being used, but the LTI 2020 has a beam of
>> about 3500meters and a 1m divergence at 1000m. At normal distances
>> this equates to about 4.5 to 8.0 cm of target area.
> Hmmm, I wonder what frequency those radars operate on. By my calculations
> using my rather rusty antenna theory to get that divergence at 3GHz you'd
> need a 130m dish antenna.
It will be a laser based one which needs a far smaller aperture to
achieve that divergence figure.

Google confirms that, but suggests a lower range.
http://www.lasertech.com/ulproduct.html
http://www.lasertech.com/Speed_Enforcement/Speed/Handheld/UL_Series.htm

There seems to be two in your second link that go out to 1km

Which suggests a lower range than "a beam of about 3500meters".

I have been stopped on the road and informed of my speed by Mr Plod but no fine and have also been fined in Richmond Park (RP) on the downhill from Ham Cross to Kingston gate. Although I think it's a 20mph limit.

If you consider the number of fast boys and girls that use RP for training it must generate a fair income.

P

Tony Raven said:

Dylan Smith wrote on 11/04/2007 10:33 +0100:

Quoted message said:

Have the police ever pulled a cyclist over in a radar trap? Have
cyclists ever set off a GATSO?

I believe it happens in Richmond Park which is one of the few places the
cyclist can commit a speeding offence. They are also widely used in
Marin County in California where Park Rangers enforce the 15mph cycle
speed limit on the trails with radar guns. Its quite difficult to keep
your speed that low going downhill.

--
Tony

"The most savage controversies are those about matters as to which there
is no good evidence either way."
- Bertrand Russell

Ziggy twisted the electrons to say:

Quoted message said:

I must say, rec's look great fun and very comfortable but I'd really
worry about my visibility if I was using one. Probably without good
reason I'll admit.

I think it's best to work up (or should that be down?) to them. Start on
something like a BikeE, then move to something like a Streetmachine and
then move to the tadpole trike!

OTOH, the taxi driver who tried to side-swipe me off the road this
lunchtime must have seen me. Since he accelerated hard to get alongside
me and then pulled sharply left so that he didn't have a head-on with
cars waiting at the traffic lights ...
--
These opinions might not even be mine ...
Let alone connected with my employer ...

Al C-F said:

Chris Eilbeck said:

There have been occasions where the police have tried to do
people for twice the speed they were actually doing because of the
radar return from the top of an advancing wheel being stronger than
that from the main bike body and rider.

Really? Would that be in the Royal Parks, or a misguided plod?

Widely reported in the motorcycling press in the mid 90s.

Quoted message said:

I would doubt very much that you could get a bigger return from a
tyre than from a whole MOTORbike.

In the early days of widespread speed guns use, they could read the
peak Doppler rather than the Doppler of the strongest return in pure
power terms. There was a Doppler vs signal strength curve built in to
the device to get round background radar clutter e.g. static
reflectors and large but slow moving targets. In some cases it read
wrong and the police tried to prosecute on the basis of this.

As I understand it, the strongest return in RCS terms comes from the
headlight reflector.

Chris
--
Chris Eilbeck

On 11/04/2007 10:33, Dylan Smith said,

Quoted message said:

Have the police ever pulled a cyclist over in a radar trap? Have
cyclists ever set off a GATSO?

I always understood that posted speed limits on roads applied only to
motor vehicles. AIUI, you can't get stopped, for instance, going at
37mph in a 30mph limit if the reason is solely your speed. If you're
weaving in and out of cars and pedestrians at the same time though, I
think the charge is "cycling furiously" or some such antiquated phrase.

Personally, I don't often have much chance to put that theory into
practise :-)

--
Paul Boyd
http://www.paul-boyd.co.uk/

Dylan Smith said:

Have the police ever pulled a cyclist over in a radar trap? Have
cyclists ever set off a GATSO?

My bro got spotted by a woodentop with a hairdryer a few years back.
Apparenrtly doing 47 in a 30.

"????" <????@????> wrote in message
news:[email hidden]...

Quoted message said:

Dylan Smith said:

Have the police ever pulled a cyclist over in a radar trap? Have
cyclists ever set off a GATSO?

My bro got spotted by a woodentop with a hairdryer a few years back.
Apparenrtly doing 47 in a 30.

You cannot say that in this group, I was called a liar for saying I had
averaged 29.5 over 84 miles!

Alan

Quoted message said:

You cannot say that in this group, I was called a liar for saying I had
averaged 29.5 over 84 miles!

....on a 3 speed tourer with front and rear panniers filled with bricks...