§ Mr. Colin Shepherdasked the Secretary of State for Transport what was the most recent comparative evaluation carried out by his Department into the high pressure sodium lamps and low pressure sodium lamps for motorway lighting purposes; and if he will set out the results showing lamplife, energy consumption, light output and installation cost.
§ Mrs. ChalkerA comparative evaluation was completed in June and the data used included:
Low pressure sodium* High pressure sodium* Bulk lamp change after 8,000 burning hours 12,000 burning hours Electricity supply cost per year per lantern £29 £40 Installation cost for lantern, control gear and 1st lamp £110 £70 Lamp cost £19 £10 * Light output assumed to be about 26,000 lumens in both cases. The conclusion was that the whole life costs were finely balanced over the life of the lantern and on that basis the low pressure sodium type should be favoured as it uses much less energy. In view of this conclusion consideration is being given to requiring evaluations to be done on a scheme by scheme basis, using tender costs, to ensure that value for money is always obtained.