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Canals and Rivers

Although the British government obtained from the EC a derogation from metric directive 89/617 for road and pedestrian signs, it omitted to exempt waterway signs meaning that, to comply with EU law, canal and river signs must give distances in kilometres and speeds in "kph" (kilometres per hour). As a result, the Environment Agency has switched to kilometre signs on rivers within its juristiction, for instance, on the River Thames.

11.2 kph
A metric speed sign, along the River Nene, to one decimal place

In many areas, however, such as the Fenland Waterways, also covered by the Environment Agency, metric conversion has stalled. This is because local byelaws specify speed limits in so many miles per hour. To convert to metric sign posting with these byelaws unchanged would mean direct conversions from existing (mile-based) speed limits to their metric equivalents. Thus, a 4mph speed limit would become "6.4 kph". Obviously, such conversions would be absurd with the result that rivers and canals covered by parts of the Environment Agency, the Norfolk Broads and British Waterways have not converted to metric.

In 1996, the Broad's Authority wrote a letter of complaint to the Department of Environment (now the DETR), pointing out that 700 signs on the Norfolk and Suffolk broads would have to be replaced at "extremely high" cost due to many being in remote riverside areas and difficult to access. The Broads Authority also stated that:

  • The great majority of the 1,500 hire cruisers based in the Broads have their engine tachographs calibrated to show boat speed in mph only. It would require the recalibration of all of these vessels, which would be an extremely onerous and time consuming exercise for the hire boat industry and private boat owners.
  • A considerable number of hire craft have electronic digital speedometers showing boat speed in mph. The design of these speedometers has been evolved by consultants for the Broads Authority which has encouraged the fitting of these to vessels. Conversion of these to show kph may not be technically feasible and would certainy be extremely expensive.
  • The Authority has published a range of informational literature promoting the importance of adherence to the Broads speed limits for the protection of the environment and safe navigation. These publications would require to be redesigned and existing stocks would be wasted.
  • The Authority's River Inspectors use radar speed detection devices to enforce the Speed Limit Byelaws. These are calibrated in mph. Conversion of these to kph is unlikely to be feasible, necessitating their replacement at very considerable cost.
  • All boat speedometers give a reading of speed "through the water", whereas all boating speed limits are based on speed "over the ground". It is therefore necessary in order to observe marine speed limits to understand and make allowance for the prevailing tidal stream. Tidal information is provided on charts and pilot books universally in knots (nautical mph) or in mph. It therefore becomes significantly more difficult to assess whether one's vessel is operating in breach of the speed limit if the limit is expressed in kph.
  • Probably most importantly, the speed limits in the Broads are 3, 4, 5 or 6 mph depending on the area. These speeds correspond to 4.8 kph, 6.4 kph, 8 kph or 9.6 kph respectively. These are very low speeds, but research has shown that they are critical speeds and that an increase of even 1 mph over these speeds would significantly increase damage to the natural environment of the Broads by boat wash. It would destroy much of the objective of the Broads speed Limit to "round up" the kph figures. It would clearly be considered a nonsense on the roads to express speed limits to one decimal place of a kph and it is likewise considered that to express river speed limits to one decimal place of a kph will be likely to provoke adverse reaction from the boating public, thereby leading to increased disobeyance of the limits.
  • Whilst with the passage of time the public will come to be as familiar with speed expressed in kph as they are with mph, that time has not yet come. For the great majority of the boating public, their effective measure of boat speed is related to walking pace which they recognise as being approximately 4 mph. Very few members of the public would be able to express walking pace in terms of kph. It follows that to express the river speed limits in kph is to present the public with an abstract concept which they will find difficult to understand. The Authority's present mph speed limits are understood by the public and are generally supported by them. Limits in kph would not have that support and the result would be widespread disregard of the limits with consequently greatly increased environmental damage to the Broads system and a significantly higher burden for the Authority in enforcing Speed Limit Byelaws.

Similar points were made by preservation groups such as the Inland Waterways Association which argued that, "...it was not the intention of Parliament to place waterway users at a disadvantage [in having to use a different system] to the rest of the general public". The IWA noted that many mile posts and stones had been listed under the Town and Country Planning Act 1971.

Both the Broads Authority and the Inland Waterways Association believe there is a legal argument (within UK law) against the metric conversion of waterways. This is based on interpretation of the wording of the Units of Measurement Regulations 1995 which state that metric conversion does not apply to: "the use of the mile, yard, foot or inch for road traffic signs, distance and speed measurement".

It could be argued that the wording means that road signs, distance and speed measurement are separate stipulations. There is certainly logic to this, since no legislator would seriously propose that roads woud use one unit of distance and speed, while waterways use a different unit. The regulations also provide for the continued use of the nautical mile and knot for sea and air traffic. In this interpretation, waterways are allowed to use the mile for distance and speed measurement.

However, when the DTI issued its Guidance Note in 1995, it used the following wording: "mile, yard, foot and inch for road traffic signs and for related distance and speed measurement". Note that the comma after "signs" is missing, and how the word "related" is inserted, the effect of which is to narrow the application of distance and speed from all forms of transport to road signs. This Guidance note has no authority in law, but it is evidence of how government departments regard themselves as higher than Parliament.

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