Re: Can someone calculate
"very few pure hybrids achieve better fuel efficiency than an equivalent-sized diesel powered vehicle."
In open road cruising that's true and unarguable.
For urban warrior work, it's a completely different story.
The issue with car engines (diesel or petrol) is that they only work efficiently at full load and even than that's only ~35% maximum and only when at operating temperature.
The average petrol engine runs around 2-4% efficiency most of the time and 0% when idling in traffic.
Stop/start engine technology has made quite a difference for dense urban traffic fuel consumption but in the suburbs where most runs are less than 2 miles in light traffic you can expect your 50mpg diesel to be making more like 25-28mpg (real world figures) - and BOTH these areas are where hybrids win.
Using a smaller, lighter engine with more tightly defined operational parameters means you can cut the emissions control weight and complexity too, so there are engine/battery tradeoffs you can exploit for a win-win situation, but don't expect to see many hybrid longhaul trucking rigs. (On the other hand hybrid trucks are ideal for drayage work)
The further advantage in dense urban environment is that you can switch the engine off entirely and roll on electric power during pollution blackouts, but it's worth noting that London's NOX levels are now only 40-45% caused by vehicle emissions and have been like this for a while (predating Euro5 cars), so you get a law of diminishing returns unless you go after the largest pollution sources.
offtopic: The largest source of NOX in London is old-school gas and oil-fired boilers and for the most part they're also the largest source of HC and particulate emissions. Modern condensing ones are almost zero emission, which is one of the unstated reasons councils trend to mandate the things but their complexity is the very thing which causes owners of older massively polluting installations to refuse to update (until they get CO poisoning and the system is condemned, as happened to some friends of mine).
That said - London NOX (and other pollution levels) are only problematic inside the inner london ring road and virtually non-existant outside the North/South circular roads. A lot of automotive pollution control technology is being produced and sold with efficiency and cost penalties everywhere, to nail issues that only occur in small areas when there are probably better ways of tackling the issues, such as adaptive technology which restricts emissions when actually needed or simply mandating zero emission vehicles in zone 1.