From: Adrian on
Cynic <cynic_999(a)yahoo.co.uk> gurgled happily, sounding much like they
were saying:

>>>>There's a rather big difference between installing a warning device in
>>>>the plane and installing a warning device on every single mountain...

>>> Next time you see a tall aerial mast, look at the top of it. You will
>>> note that it has a flashing red beacon. Guess why that's there.
>>>
>>> And those are fitted to *every* tall mast.

>>Aerials are difficult to see.
>>Mountains are easy to see.
>>
>>Can you guess which end of that spectrum bridges fall under?

> The height of a bridge is just as easy to see as the minimum sector safe
> altitude on an aeronautical chart.

If you happen to be looking at said chart, yes. I'd have said that was
rather less of a constant activity for a pilot than looking out of the
windscreen should be for a driver. A chart also presupposes the pilot
being fully aware of his location.
From: Cynic on
On 23 Dec 2009 15:44:58 GMT, Adrian <toomany2cvs(a)gmail.com> wrote:

>>>Aerials are difficult to see.
>>>Mountains are easy to see.
>>>
>>>Can you guess which end of that spectrum bridges fall under?
>
>> The height of a bridge is just as easy to see as the minimum sector safe
>> altitude on an aeronautical chart.
>
>If you happen to be looking at said chart, yes. I'd have said that was
>rather less of a constant activity for a pilot than looking out of the
>windscreen should be for a driver. A chart also presupposes the pilot
>being fully aware of his location.

You only need to glance briefly at a chart once to find the minimum
safe altitude for the sector you are about to enter - they are written
in rather large figures that, in your words, the pilot would have to
be blind or brain-dead to miss seeing. No need for it to be a
constant activity.

A pilot should not get lost. In your World, we should not make any
efforts to cater for contingencies that should not happen. Especially
expensive things like fitting high power lamps and wasting electricy
to keep them lit all the time.

--
Cynic

From: Cynic on
On 23 Dec 2009 15:47:11 GMT, Adrian <toomany2cvs(a)gmail.com> wrote:

>> If the only circumstance in which you can envisage a driver failing to
>> notice a single road sign is if he is blind or brain dead, then I pity
>> your ignorance of even the basics of human factor considerations.

>Not quite. They're the only circumstances in which I can envisage the
>driver of a tall vehicle proceeding under a bridge that he can see looks
>low without at least thinking that a check might be advisable.

I can well believe that that is the only circumstance that *you* can
envisage. Which is why I know that you are ignorant of even basic
human factor considerations.

--
Cynic

From: Roland Perry on
In message <t492j5h6tucglm1uehlqgbtma47u7umc1u(a)4ax.com>, at 20:00:36 on
Tue, 22 Dec 2009, Cynic <cynic_999(a)yahoo.co.uk> remarked:
>Maybe you should remove all the safety equipment from your car and fit
>a huge spike to the centre of the steering wheel. After all, provided
>you never make a mistake, you'll be no worse off.

Unfortunately, about half the relevant mistakes are made by someone
else.
--
Roland Perry
From: Denis McMahon on
Adrian wrote:

> Where did I say that sensible precautions weren't required? I'd have said
> a compulsory sign in front of every low bridge and a compulsory notice in
> the cab of every tall vehicle were such sensible precautions.

Evidence (people driving overheight vehicles into bridges several times
a year) suggests that these simple precautions may not prevent all such
collisions happening that could be prevented.

I've already suggested possible reasons:

1) Drivers who are used to fitting under any bridges on their "normal"
route becoming desensitised to low height signs and then having to use
unfamiliar roads.
2) Drivers being distracted on approach to a low bridge and as a result
not processing the low height warning amongst other distractions they
are attending to.

I postulate that the most likely cause of such collisions is that the
driver didn't notice, or didn't realise the significance of, the warning
sign. Either because he was distracted by something else, or isn't in
the habit of noticing such signs and doesn't therefore attach importance
to them.

This 2005 story

http://news.bbc.co.uk/1/hi/england/lincolnshire/4509806.stm

suggests that the problem is pretty widespread, it also suggests that
some bridges are more susceptible to the problem than others. I seem to
recall that before the Petersfield - Liphook bypass was built on the A3,
there was a railway bridge just South of Liphook (now on the B2070) that
had a few collisions every year.

It's interesting that according to that report, some drivers manage to
ignore "collision protection beams and chevron marking and improved
signage" - presumably by collision protection beams they are referring
to an optical overheight detection coupled with a warning system.

Maybe such systems should use red traffic lights positioned before the
bridge?

Rgds

Denis McMahon
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