Update: As commenters below have pointed out, the data may not be comparable enough between the two countries to draw such a strong conclusion, for reasons of definitions and possible different rates of under-reporting. See new post on the topic here.
I used data from the Dutch road safety research institute SWOV yesterday to compare cycle fatality rates in the Netherlands with those in Britain, and Mark pointed out on Twitter that SWOV data also breaks down the number of casualties according to whether or not any motor vehicles were involved. This is handy, as it allows us to see whether the low cycle casualty rate in the Netherlands is due to (a) fewer collisions with motor vehicles or (b) fewer casualties from collisions with pedestrians, other bikes or cyclists just crashing into stuff or (c) all of the above.
This table indicates that 64% of serious or fatal cycle casualties in the Netherlands are the result of collisions with motor vehicles*. This compares with 91% in Britain, from this DfT table**.
We saw yesterday that the cycle fatality rate per km is more than twice as high in Britain as in the Netherlands. According to SWOV data the gap is even larger when you include serious injuries: in Britain there are 556 cyclists killed or seriously injured for every billion kilometres cycled, compared to 96 in the Netherlands (in both cases I'm using the most recent year available, 2009 for the Netherlands and 2010 for Britain).
Put these figures together and you get the chart below, which shows that the rate of serious or fatal cycling casualties not involving motor vehicles is actually reasonably similar in the two countries, 35 per billion km in the Netherlands compared to 49 in Britain. But the gap for collisions with motor vehicles is huge: just over 500 British cyclists are killed or seriously injured in collisions with motor vehicles for every billion km cycled, over eight times the rate in the Netherlands.
I think this shows just about as starkly as possible the consequences of two different approaches to cycling: one which expects cyclists to constantly mix with heavy and/or fast-moving traffic, and one which doesn't. In the Netherlands they very carefully and deliberately try to reduce the chances of a serious collision between motor vehicles and cyclists, and you know what, it looks like it works. In Britain we don't try very hard to do that, and we get the results you see above.
* Select 'Bicycle' under 'Mode of transport' and then nest the 'Type of accident (E-code)' variable in the rows. There are a lot of blanks ('Not matched') under 'Type of accident' for fatalities, so I just calculated the percentage based on the non-blank records)
** Scroll over to 'All areas' and tot up the pedal cyclists killed or seriously injured in collisions with other cycles, pedestrians, or in single vehicle, no pedestrian accidents. The remainder are the results of collisions with motor vehicles.