Question to the Department for Transport:

To ask the Secretary of State for Transport, with reference to the Answer of 31 March 2014, Official Report, column 408W, on High Speed 2 Railway Line, what the evidential basis for double-decker carriages not releasing sufficient capacity for commuter services is.

As per the answer of 31 March 2014, since 2009 we have considered a wide range of alternative options to a high speed railway including the use of alternative modes, a conventional speed line and upgrades to the existing rail network, including double decking.

Specifically, the March 2010 High Speed 2 Strategic Alternatives Study considered the potential for using double deck trains on WCML as one means of enhancing capacity on conventional rail routes between London and the West Midlands/North West. Details of this study, including evidence of expense, disruption and capacity, can be found at:

http://webarchive.nationalarchives.gov.uk/+/http:/www.dft.gov.uk/pgr/rail/pi/highspeedrail/alternativestudy/pdf/railintervention.pdf.

This work found that while double deck carriages could increase the number of passengers per train there is a practical limit to the expansion of capacity in this manner and it offers limited potential to lead to journey time savings.

This option is also likely to lead to significant disruption and expense. Before such trains could be used on the West Coast Mainline, the route (including diversionary routes) would need to be gauge cleared to allow sufficient space for the trains to operate. This would involve raising all overhead wires, raising bridges, modifying platforms on the route, modifying station canopies, moving or raising all signal gantries and other signage on the route, and lowering track in the tunnels. Work would need to be carried out to modify existing depots or to provide new ones. Additional works would also be required to enable line speeds to be maintained on the route.

For these reasons it was concluded that there was a strong case for not considering this option further. No subsequent work has therefore been done to compare it to the case for HS2.