On 11/09/2017 10:12, TMS320 wrote:

On 09/09/17 21:29, JNugent wrote:
On 09/09/2017 12:40, TMS320 wrote:
On 09/09/17 00:39, JNugent wrote:
On 09/09/2017 00:32, TMS320 wrote:
On 08/09/17 13:39, JNugent wrote:
On 08/09/2017 11:39, TMS320 wrote:

Perhaps what is needed to reduce close passes outside shop
doors are obstructions on the pavement, such as plant
troughs... or free to use bicycle pumps.

Or occasional cattle grids, arranged longitudinally in line
with the direction of pedestrian travel.

Possibly, though putting something down with no purpose other
than to trap and cause harm might be rather harsh.

The purpose would *not* be to trap or harm anyone. Everyone
already knows that cycling is not permitted on footways and in
other pedestrian-only areas.
Preventing cycling along footways by physical means is no
different in principle from placing obstacles to prevent
motor-vehicles with three or more wheels from being driven onto
footways or into specified pedestrian zones.

I have not yet seen an obstacle for motor vehicles that intentionally
traps the wheels.

The Denver Boot makes a fair attempt at it. But there are other built-in
traps which dole out damage to vehicles which is usually
disproportionate to the "offence" being deterred. Those "rising
bollards" used for controlling access to urban pathways for buses and
delivery vehicles, for instance, have been known to do severe damage to
bodywork and floorpans. There have been a few internet videos of such
incidents. They are, at the very minimum, at least analogous to
cattle-grids. And probably more dangerous to humans.

If you want prevention you stop or discourage people from going
where you don't want them to go. Prevention is not about harming
them if they go there.

No-one will harm them.
They might harm themselves, just as they will if they try to cycle
through a locked gate, or a brick wall.

The primary purpose of such things is not to trap or cause harm.

Quite right; it's a secondary effect. And the primary purpose of a
cattle grid placed inline on a footway would be to deter cycling on that
footway. Not different in principle to a "kissing gate or to the
obstacles which are to be found in the Greenwich *Foot* Tunnel in a vain
attempt to get cyclists to behave lawfully.

Your suggestion is rather like fitting RPGs to speed cameras.

Not in the slightest.

Harm from a speed camera mounted RPG would only be self inflicted.

Please describe the triggering and logic systems, detection process,
rocket-propulsion and warhead strength in some detail, together with the
anti-error provision. How many nearby pedestrians woild be killed with
each firing and what level of collateral damage to other vehicles and
buildings would have to occur for it to be unacceptable to you?
Sensible people would not oppose that measure in either case.

Many people that don't ride bicycles aren't sensible about
cycling.

You said it.

If your idea came about, children and pensioners would be caught in gaps
smaller than needed to stop bicycle tyres from skimming over. Perhaps
"sensible" in your world means a regular occurrence of hip and ankle
injuries is worthwhile in order to stop one scum cyclist.

Just one?

Anyway, the gaps would only need to be about 1.5" wide (and a foot
deep). When was the last time you heard of anyone being injured walking
over a cattle-grid? No, me neither.