(23 Apr 2015, 9:57 pm)idiot wrote I'm shocked!
But, the operators get enhanced 'credits', via central government, due to their lower carbon emissions. So the difference is enhanced slightly.
This link (http://www.lowcvp.org.uk/initiatives/lce...oolkit.htm), is useful.
It may also explain why battery operated buses (such as those seen on the Quaylink in years gone by), haven't proven that successful