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know the law
Page 98
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by Les Oldridge AIRTE, AMIMI
Abnormal loads (2)
with from 10,001 to 25,000 delivery points. Another question revealed that three firms with 26 to 100 distribution centres have more than 100,000 delivery points. It is not hard to imagine that in this league vehicle scheduling for maximum economy does represent a major headache.
How many delivery points can be served from one distribution centre? Twenty-one firms (40 per cent of those questioned) said from 1001 to 5000; 11 firms said they delivered to over 5000 customers from a single distibution centre.
What types of firm are most interested in vehicle scheduling by computer? Thirty-five per cent of firms questioned in the food and drink category expressed interest compared with 20 per cent for chemicals, etc. Retail deliveries prompted only 13 per cent response and engineering 10 per cent. Interestingly, the commodities mentioned are classified according to the Standard Industrial Classification as used in an NCC survey on distribution published in 1968. (See Management Matters April 24.) Some of the information in the NCC survey, as recorded in the questionnaires, is fascinating. On vehicle types, used, for example (types meaning vehicles of different carrying capacities or of basically different design for storing merchandise) 41 per cent of firms questioned used from five to 10 different types and four firms used over 50 different types! That sounds as if they comprise the ICI or Unilever complex.
The practical difficulties of vehicle scheduling by computer will be very obvious to experienced transport managers but considerable momentum is building up to the use of computers for trip-planning. The constraints—legal working hours, vehicle capacity restrictions, limited access to customers, etc, speak for themselves. What are described as "negative" constraints provide teasing problems for the boffins: the normal "give-and-take" between supplier and customer; part-delivery of orders; delivery outside specified hours; delivery with a different type of vehicle; anomalous early closing days, etc.
Other constraints impose themselves on the computer program because they involve calculations during the running of the computer and may impose restrictions on the program because of limitations on core size. Journey times can be calculated before the computer run with the aid of very accurate work study values; but the matrix of journey times between any pair of points requires much calculation "and may be the cause of considerable wasted effort since many of the values will not be required during computation. . . ". Journey times worked out during a run involve rules which give no more than approximate times and distances.
Distance calculations involve the application of a correction factor. to crow-fly mileages calculated by Pythagoras's theorem. Some programs utilize predetermined mileage calculations between most frequently used points. Give the computer men time, and sufficient compatible hardware and software, and every road excavation or route diversion may be taken account oft HAVING considered maximum lengths and widths of vehicles permitted under the Motor Vehicles (Authorisation of Special Types) General Order, 1969, in the previous article it is now necessary to deal with the maximum weights allowable.
The sum of the weights transmitted to the road surface by all the wheels of the vehicle or vehicles must not exceed 150 tons and no one wheel must transmit a weight exceeding 11+ tons. Where axles are not more than 211 apart the wheels on each axle must not carry a total of more than 45 tons. Axles which are more than 2ft apart but not more than 711 apart may have additional loads at a rate of 9 tons per foot. Axles more than 7ft apart may have additional weight at a rate of 3 tons per foot.
All wheels must be fitted with pneumatic tyres or tyres of soft or elastic material (ie solid rubber tyres). In the latter case the total weight transmitted to the road surface by any wheels in line transversely must be such that the average weight per inch width of tyre in contact with the road surface does not exceed 15cwt.
The limit of 11+ tons per wheel does not apply to a heavy motor car registered on or before December 31, 1951, or to a trailer manufactured before January 1, 1952. Wheels less than 211 apart are to be regarded as a single wheel.
Normally only one indivisible load may be carried at any one time, but if the Construction and Use requirements are complied with in respect of laden weights and weights transmitted to the road surface then more than one load of the same character may be transported.
Speed restrictions
Vehicles specially authorized by Article 20 of the Order are restricted as to speed. When not carrying a load and complying with the C and U Regulations with respect to wings, springs, brakes, tyres and weights the speed is limited to 20 mph provided its width does not exceed 911 6in. Otherwise there is a speed limit of 12 mph. These speed limits do not apply on special roads.
One attendant is required if the load is between 2.5 metres (8ft 2+in.) and 9ft 6in. wide; if the load is wider than this two attendants are needed. One attendant is also required if the overall length of the vehicle, inclusive of projections of the load to the front or rear. exceeds 60ft, or if the loads project more than 6ft to the front or 10ft to the rear. Attendants are to be in addition to the driver and have to attend to the vehicle and its load and to give warning to the driver of the vehicle and to any other person of any danger likely to be caused by reason of the use of the vehicle.
Attendants required by Section 72 of the Road Traffic Act 1960 to attend to trailers count for this duty, but driver(s) of a second vehicle assisting in the propulsion of the outfit do not. The requirements for two attendants does not apply if the vehicle is moved on a road no more than is necessary for the efficient performance of engineering work on which it is engaged, one attendant being sufficient under these circumstances.
Projections
Article 25 of the Special Types Order deals with the marking of projecting loads on vehicles carrying abnormal loads. If the load projects forward more than 611 or rearward more than 10ft then marker boards as laid down in Schedule 8 to the C and U Regulations must be displayed. If the projection to the rear is more than 3ft 6in. but less than 10ft it must be made clearly visible. No particular method of making it visible is laid down but a flag or rag tied to the projection or having it brightly painted would suffice.
Where there is a projection to the front or rear of one vehicle and another vehicle is attached to it so that there is no projection over the second vehicle then the projection need not be marked. If the load projects beyond the second vehicle than it need only be marked according to the length of the projection heyand the second vehicle. Vehicles used for the purposes of the police, fire brigade, ambulance, defence or removal of traffic obstructions are exempt from these marking requirements if compliance would hinder the purpose for which they are being used.
The marker boards referred to are the familiar white triangles with red stripes and border, as required for vehicles with projecting loads used under the C and U Regulations. The boards must be illuminated at night by means of lamps sufficient to render the boards readily distinguishable from a reasonable distance. These lamps must be shielded so that only light reflected from the surface of marker boards is visible.