Mechanical and electrical (M&E) systems in road tunnels are constrained by the traffic envelope and the construction profile. Whilst these spatial constraints are often locked in' early in the design process, the detailed M&E design continues for some considerable time after key civil engineering issues have been resolved._x000D_
Ventilation design criteria for both normal and emergency operation often involves considerable negotiation with a wide range of stakeholders. Final system performance and spatial requirements are only finally resolved when suppliers are selected following the tender process._x000D_
Lighting design is dependent upon a wide range of factors including tunnel lining materials and associated colours as well as agreed maintenance regimes._x000D_
Cabling systems can only be developed when the general arrangement for power distribution is agreed and a system of substation, switchrooms and equipment rooms is in place._x000D_
Many other systems such as fire protection and communications facilities fill the available space beyond the traffic envelope, where physical, structural and sight line' requirements must all be accommodated._x000D_
The more co-ordinated civil engineering and M&E design is and the earlier the process starts the better the outcomes for all parties.