On Thu, 29 Jul 2010 14:28:53 -0700 (PDT),
" wrote:

On 29 July, 15:15, wrote:
On Thu, 29 Jul 2010 15:01:56 +0100


Paul Terry wrote:
In message , David Walters
writes

On Thu, 29 Jul 2010 14:08:34 +0100, Paul Terry wrote:

Added to which, it has been widely reported (and confirmed by the
cameras' manufacturer) that drivers can defeat a SPECS camera by the
potentially unsafe practice of lane-hopping during the measured section
of road.

That hasn't been the case since sometime in 2007.

http://www.theregister.co.uk/2008/07...d_camera_myth/

Ah, glad to hear that that loophole has been closed.

Did anyone believe it worked anyway? Why would anyone writing the software
make the cars lane part of the database key in the first place? It makes
no sense whatsoever.

Possibly for the sake of simplicity to allow for e.g. the difference
in speed between two vehicles remaining in parallel in lanes 1 and 4
where there is a significant curve between measurement points. If the
usual 10% etc. tolerance is ignored and speed limits applied strictly
then in theory it would be possible for the two vehicles to stay
together with one under and one over the speed limit.

The best way of deafeting specs cameras is just remove your front number plate
which I've done on many an occasion. Or ride a motorbike.

B2003

The cameras being installed as part of the extended trial here face
both ways, and a colleague of mine has just fallen victim to them.
Alerted the patrol officer that his rear number plate was too small
and he got stopped three miles down the road. One biker who claimed he
would never be stopped.

On Fri, 30 Jul 2010 07:23:26 +0100
Charles Ellson wrote:
Did anyone believe it worked anyway? Why would anyone writing the software
make the cars lane part of the database key in the first place? It makes
no sense whatsoever.

Possibly for the sake of simplicity to allow for e.g. the difference
in speed between two vehicles remaining in parallel in lanes 1 and 4
where there is a significant curve between measurement points. If the
usual 10% etc. tolerance is ignored and speed limits applied strictly
then in theory it would be possible for the two vehicles to stay
together with one under and one over the speed limit.

In theory , but it would have to be one hell of a small radius curve to make
a significant difference. Not something you're likely to find on the sort
of roads these cameras are placed on.

B2003

In article , d
wrote:

On Fri, 30 Jul 2010 07:23:26 +0100
Charles Ellson wrote:
Did anyone believe it worked anyway? Why would anyone writing the software
make the cars lane part of the database key in the first place? It makes
no sense whatsoever.

Possibly for the sake of simplicity to allow for e.g. the difference
in speed between two vehicles remaining in parallel in lanes 1 and 4
where there is a significant curve between measurement points. If the
usual 10% etc. tolerance is ignored and speed limits applied strictly
then in theory it would be possible for the two vehicles to stay
together with one under and one over the speed limit.

In theory , but it would have to be one hell of a small radius curve to make
a significant difference. Not something you're likely to find on the sort
of roads these cameras are placed on.

No it wouldn't - the difference in distance only depends on the
difference in heading between the start and end points.

Sam

On 30/07/2010 16:03, Sam Wilson wrote:
In , d
wrote:

On Fri, 30 Jul 2010 07:23:26 +0100
Charles wrote:
Did anyone believe it worked anyway? Why would anyone writing the software
make the cars lane part of the database key in the first place? It makes
no sense whatsoever.

Possibly for the sake of simplicity to allow for e.g. the difference
in speed between two vehicles remaining in parallel in lanes 1 and 4
where there is a significant curve between measurement points. If the
usual 10% etc. tolerance is ignored and speed limits applied strictly
then in theory it would be possible for the two vehicles to stay
together with one under and one over the speed limit.

In theory , but it would have to be one hell of a small radius curve to make
a significant difference. Not something you're likely to find on the sort
of roads these cameras are placed on.

No it wouldn't - the difference in distance only depends on the
difference in heading between the start and end points.

The _absolute_ difference in distance (i.e. measured in metres) only
depends on the difference in heading between the start and end points
_and the radial distance between the midpoints of the two lanes in
question_.

However, the relative difference in distance (i.e. the percentage of the
total distance) depends on the total distance travelled. To get a
significant percentage difference in distance (and hence speed), the
change in heading must be done in a short distance, and this implies a
tight curve.
--
Jeremy Double {real address, include nospam}
Rail and transport photos at
http://www.flickr.com/photos/jmdoubl...7603834894248/

In article ,
Jeremy Double wrote:

On 30/07/2010 16:03, Sam Wilson wrote:
In , d
wrote:

On Fri, 30 Jul 2010 07:23:26 +0100
Charles wrote:
Did anyone believe it worked anyway? Why would anyone writing the
software
make the cars lane part of the database key in the first place? It
makes
no sense whatsoever.

Possibly for the sake of simplicity to allow for e.g. the difference
in speed between two vehicles remaining in parallel in lanes 1 and 4
where there is a significant curve between measurement points. If the
usual 10% etc. tolerance is ignored and speed limits applied strictly
then in theory it would be possible for the two vehicles to stay
together with one under and one over the speed limit.

In theory , but it would have to be one hell of a small radius curve to
make
a significant difference. Not something you're likely to find on the sort
of roads these cameras are placed on.

No it wouldn't - the difference in distance only depends on the
difference in heading between the start and end points.

The _absolute_ difference in distance (i.e. measured in metres) only
depends on the difference in heading between the start and end points
_and the radial distance between the midpoints of the two lanes in
question_.

However, the relative difference in distance (i.e. the percentage of the
total distance) depends on the total distance travelled. To get a
significant percentage difference in distance (and hence speed), the
change in heading must be done in a short distance, and this implies a
tight curve.

Good point!

Sam

On 30/07/2010 07:23, Charles Ellson wrote:
On Thu, 29 Jul 2010 14:28:53 -0700 (PDT),
"jonporter1052@btint ernet.com wrote:

On 29 July, 15:15, wrote:
On Thu, 29 Jul 2010 15:01:56 +0100


Paul wrote:
In , David Walters
writes

On Thu, 29 Jul 2010 14:08:34 +0100, Paul Terry wrote:

Added to which, it has been widely reported (and confirmed by the
cameras' manufacturer) that drivers can defeat a SPECS camera by the
potentially unsafe practice of lane-hopping during the measured section
of road.

That hasn't been the case since sometime in 2007.

http://www.theregister.co.uk/2008/07...d_camera_myth/

Ah, glad to hear that that loophole has been closed.

Did anyone believe it worked anyway? Why would anyone writing the software
make the cars lane part of the database key in the first place? It makes
no sense whatsoever.

Possibly for the sake of simplicity to allow for e.g. the difference
in speed between two vehicles remaining in parallel in lanes 1 and 4
where there is a significant curve between measurement points. If the
usual 10% etc. tolerance is ignored and speed limits applied strictly
then in theory it would be possible for the two vehicles to stay
together with one under and one over the speed limit.

Do the maths... the standard lane width on a motorway is 3.65 m, so the
maximum extra distance, even assuming the motorway does a 90 degree
turn, is 3 * PI/2 * 3.65 or about 18 metres. Assuming the average speed
cameras are fairly close, say 1/2 mile (or 800 m), this is only 2% of
the distance (and hence a difference in speed of 2%).

In practice, there aren't many (any?) motorways that do a 90 degree
curve in 800 metres, so the difference in speed would in practice be
less than this.
--
Jeremy Double {real address, include nospam}
Rail and transport photos at
http://www.flickr.com/photos/jmdoubl...7603834894248/