My postman tells me that Royal Mail recently took delivery of new Fiat vans fitted with diesel particulate filters. Now postal workers on suburban stop-start 'walks' are sitting revving the engines to simulate longer, faster journeys. This wastes both time and fuel but prevents the engine management system detecting a problem and putting the engine into 'limp home' mode. Fiat apparently replaces one DPF under warranty. After that it's an expensive owner responsibility. An example of fleet mis-management, perhaps?