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Approach hump-backed bridges in safety
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Hump-backed bridges can be very dangerous if you don't approach them with respect, as you can't see oncoming traffic. There are a few near me that are dangerous even when approached by both drivers travelling at 5 mph as they're so steep that your bumpers are nearly touching by the time you can see one another ..... and most of them are single track, too.

Ironically, these bridges are much safer at night, because you can see the other driver's headlights.

There are two forms of the bridge-o-scope:

The basic form consists of a large metal duct with angled mirrors and big prisms at each end. It is fitted on one side of the bridge. The scope is so aligned that an approaching driver can see the road on the other side of the bridge through the scope. The system is purely passive.

The active form of the scope has a yellow light facing each way down the road, and a doppler radar detector, as used on traffic lights. As you approach the bridge, the yellow light on the opposite side illuminates, warning approaching drivers.

I am advocating this idea only for those bridges which are so narrow and steep as to pose a hazard even to careful, cautious drivers. The idea is not intended as a substitute for driving courteously and with due care and attention.

8th of 7, Jul 01 2002


       Another passive solution would be a large horizontal, metal mirror hanging over the higest point.
FarmerJohn, Jul 01 2002

       I like the active warning - very bakeable, very useful. At low traffic volumes this could replace the traffic lights used at certain dangerous bridges - works in a similar fashion, but generates a 'give way' warning, rather than a stop/go command. Bias it in one direction and thar she blows.
drew, Jul 01 2002

       A convex mirror on a post by the side of the road, at the peak, have been around for years. Great in the day, and good with headlights as well. They too are used where a sharp descent and/or intersecting angled road T's onto another road.   

       Nice idea 8/7 for the ducted mirror prisms, although the K.I.S.S. philosophy says its a little overkill. The lensing system would have to allow trucks and TVR's alike to have the same degree of view.
Johnny Mash, Jul 01 2002

       My first thought was the same as [FarmerJohn]'s, but you could do this with motion-sensing street lights (turn on when a car is about to pass underneath) too.
phoenix, Jul 01 2002

       I have seen traffic signals installed at such bridges; while they are often of the non-sensor type (allow traffic one way for 20 seconds; full-stop for 10 seconds; other direction for 20 seconds; full-stop for 10 seconds) adding sensors should not be difficult on any such bridge with enough traffic to merit such. A sensor-equipped traffic signal would probably be better than your proposed yellow lights, since it would unambiguously indicate who was supposed to proceed across the bridge and who was to wait.
supercat, Jul 02 2002

       Johnny Mash: They've put up some of those convex mirrors already, but because of the steep bridge ramps and odd approach angles (those 18th century canal buiders just gave no thought whatsoever to the needs of the motor car) they really don't work very well at all. Hence the mirror/prism/duct scheme. A simple mirro just doesn't do the job.   

       Supercat: Some bridges have this, but it's "too expensive" for some of the low traffic volumes on back roads. Or so we are told.
8th of 7, Jul 02 2002

       I think the approach to the bridge should be modified such that the minimal view over the bridge is reduced to almost nothing. This will cause drivers to be really careful and creep over the bridge very slowly. Perhaps putting the bridge on a hairpin bend with tall hedgerows on the approach would do it. My fear is that installing anything like mirrors to improve visibility will just cause traffic to speed up and result in the same carnage level as at present.
hippo, Jul 02 2002

       Hippo speaks the truth. No matter what changes are made to cars, regulations, laws, road designs etc, (or even medical science) the death rate remains approximately constant per driver/day. Which means people overall automatically adjust their level of caution, to what they are comfortable with. Since I cannot drive a car, I am in a perfect position to observe.
pfperry, Jul 02 2002

       Hippo: The bridges are already like that. The approach ramps slope upwards at about 30 degrees; that means that however slowly you come at them, you can be bumper-to bumper with an equally slow moving oncoming car before your sightline crosses the apex of the hump. Then one of you has to back up.   

       I do agree with the point about driver behaviour, but I don't see what could be done to make these bridges any more dangerous than they are. The tall hedgerows and the bends are already in place.
8th of 7, Jul 02 2002

       Yeah Baby, I'll have yer Ol' Man's XKE Roadster back in no time *FLAT*
thumbwax, Jul 02 2002

       The obvious solution is to construct the bridges out of transparent alumin(i)um.
waugsqueke, Jul 02 2002

       UnaBubba: Ooooh, yes ! Sit in the pub garden and watch the cars flying over the bridge ...... better than the telly, and gets you out in the fresh air, too.   

       Waugsqueke: Transparent Aluminium would work a treat. I suggest you implement this idea forthwith. And after you have demolished the irreplaceable 18-th century hand-built masonry structure, we will all be happy to attend the ceremony at which the nice people from the National Heritage Conservation Trust hang you by your testicles from a sour apple tree, using genuine 18-th century style hand made hemp rope, and with an authentic Morris Dancing troupe to enliven the occasion. I can't wait.
8th of 7, Jul 02 2002

       Your idea is admirable, but one better would be to construct the bridge out of grated metal, angled so that the driver can simply look through the bridge to see oncoming traffic. Of-course this would only be used on future bridges because there is no point in replacing a perfectly good one. Once again, great idea.
iambersson, Mar 02 2006


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