Driving down a road where appropriate signs warn the driver that he cannot continue is an offence of driving without due care and attention...
furnessvale and Spartacus are correct, there is no offence involved in simply driving past a warning sign (a triangular one). The key word is "warn" - the sign warns that there is a hazard ahead, but do not prohibit vehicles being driven past them.
In fact furnessvale is wrong to say it is an offence if the driver "attempts to pass under the bridge" if the signs are only triangular warning ones. It would probably only become an offence if the vehicle strikes the bridge and causes damage to it.
To illustrate the point, in some cases arch bridges are signed with two different sets of warning signs indicating different clearance available over different widths of the carriageway. A narrower vehicle can safely pass under an arch bridge (especially if in the centre of the road) when a wider vehicle of the same height couldn't. This approach wouldn't be possible if it were an offence as you describe.
The height indicated on a triangular warning sign is worked out in accordance with Chapter 4 of the traffic signs manual. It takes into account vehicles of the maximum dimensions permitted by the construction and use regulations and the possibility that a long vehicle will need greater headroom if its length spans over a dip in the road under the bridge. (a shorter vehicle would need less headroom).
Because of the numerous combinations of width and length the aim of the warning sign methodology for low bridges is to make drivers aware a hazard exists and then leave it up to them to determine whether or not their vehicle can safely pass under the bridge. The advantage of this approach is that it is not necessary to provide exemptions from a mandatory restriction for vehicles legitimately needing to travel on that road (e.g. to access property).
Passing a
mandatory sign (circular) is an offence unless exemptions apply. Because it is difficult to manage and sign exemptions, it was generally the case that traffic authorities avoided the use of prohibitory height restrictions.
However, in the last decade or so the guidance and practice on bridge signing has shifted towards distinguishing between arch bridges and beam (non-arch) bridges. If a bridge has more or less equal clearance under all parts (non-arch) then Chapter 4 recommends the use of prohibitory signs, noting that a traffic regulation order is not required for signs
at the bridge. An order
would be required if the signs are placed at some distance from the bridge, and this order is unlikely to be made if it prohibits access to property.
...or worse if the driver acknowledged that he/she was aware that the vehicle was not authorised to travel on that road.
On the contrary, having seen and been aware of warning signs may be a valuable part of a defence against a charge of driving without due care and attention.
Not seeing the signs is indicative that insufficient care and attention was given.
But the vehicle would only be not authorised to travel on that road if there was a mandatory prohibition (circular signs).
In fact - without wishing to be pedantic - a fundamental principle of highway law is that the right to pass and repass is automatic, unless expressly prohibited. A driver doesn't need to be authorised to drive on a particular (public) road, they only need to refrain from driving on a road their vehicle has been
prohibited from using. The onus in on the traffic authority to inform the driver (through the use of signs) that such a prohibition exists. This is an important point, as it explains why vehicles would be allowed to drive down a road to access property, even if through passage is prevented by a low bridge.
We are generally talking about HGVs/PSVs here so the obstruction and disruption called by such a vehicle turning around would also be considered a traffic offence.
It would only be an offence for sure if that length of road had a prohibition on making u-turns, or was a one-way street. (although no offence would occur if the driver was acting under instructions from an authorised person e.g. police officer in uniform)
The offence of obstruction is one which is subject to a test of reasonableness. Unless the driver had a history of previous convictions, a charge of obstruction caused while the driver turned their vehicle around to avoid driving under a low bridge would almost certainly be laughed out of court.
Ultimately, a person who by their actions demonstrates that they have insufficent attention to or knowledge of either their vehicle and/or what road signs are should need to retake their test.
Knowledge and understanding of highway law and traffic signs is indeed woeful. Sadly the courts and driving test system doesn't have the capacity to deal with all the people who need to retake their tests.
If their is an industrial address beyond the warming sign, then the road beyond should have warnings of 'No Through Road for High Vehicles'.
This in itself would be unlawful. Such signs would need special authorisation from the relevant national authority, which is unlikely to be granted as there is already a standardised method of signing for this situation. (as laid out in Chapter 4)
Also, as part of the problem with bridge strikes involves drivers who are unfamiliar with UK signs and possibly limited proficiency in English, the use of worded-warning signs stating 'No Through Road for High Vehicles' would be a recipe for disaster and contrary to the preferred approach of using standardised pictograms.
(apologies to all for making a long first post, this is a subject I have a special interest in.)
