One of the more curious things about the motor industry these days - well, I think it's curious - is that an apparently disproportionate amount of creative thinking is going into the design of compact MPVs, a particularly functional type of vehicle which you might not think anyone would get excited about.Ford's latest offering in this sector is the Fiesta-based B-MAX, which differs from its rivals in having sliding rear doors. There is no central pillar (instead, all the doors hook on to a metal catch whose rough welding was the subject of some comment at a recent press event) but if you're concerned about possible safety implications it's worth noting that Euro NCAP has given the B-MAX its top five-star rating for crashworthiness.Specifically, maximum points were awarded for adult protection in a side-on impact with a barrier. When the object impacted was a pole, protection of the driver's chest was rated as "marginal", which I suppose is okay considering what an alarming event sliding sideways into a pole must be.This level of protection is possible because, when the two doors on each side are shut, their inner structures combine to create something that replaces the non-existent pillar. That will certainly aid the car's overall structural integrity, and while we're on the subject it should be stressed that you should make sure the doors are closed if you jack up the car to change a wheel. I have heard no suggestion that failing to do so would cause damage, but I can quite believe that it would.When I first looked at a B-MAX with all the doors open it occurred to me that getting into the back might be a bit of a squeeze for a tall fellow like myself, but in fact it's easy enough, and there is plenty of room for four six-footers.Luggage space, depending on what you do with the rear seats, is between 304 and 1372 litres if you correctly specify a spare wheel, or between 318 and 1386 litres if you wrongly opt for a tyre repair kit. The floor is higher than seems necessary, but if can be removed to reveal more space underneath. All the seats (yes, including the front ones) can be folded flat with one pull of a lever, so the B-MAX can carry a 2.3-metre long load.All this is respectable enough, but it's worth looking at the car's rivals. According to Ford, these consist of the Citroen C3 Picasso, the Honda Jazz and the Nissan Note, though the Note is an unfairly easy target since, delightful as it is, it's a very much older design and will be replaced in the near future.Ford says that it does not see the Vauxhall Meriva (another compact MPV with an innovative door arrangement) as a rival, on the official grounds that the Meriva is more popular with fleet customers while the B-MAX is aimed at private buyers. Sure enough, around 80% of Merivas sold in the UK are bought by fleets, but that still leaves room for the possibility that a retail customer will consider choosing between the Vauxhall and the Ford, so in my view the two are competing against each other.Well, then. With seats-up luggage capacity of 397 litres, the Meriva is handsomely roomier than the B-MAX, partly because it's longer. But this isn't a Vauxhall walkover. The C3 Picasso, almost exactly the same length as the Ford, offers 385 litres, the Jazz, nearly seven inches shorter, 379 litres. And two cars not mentioned at all by Ford, the Kia Venga and Hyundai ix20, neither of them my favourite products of their respective builders, manage 440 litres. With all this in mind, Ford's claim - as quoted in Tom Stewart's launch review - that it has "class-leading loadspace" looks frankly silly.This test is slightly unusual in that it involved me driving two apparently identical cars. If I were writing only on the basis of driving the first one, I would be moving into sharply critical mode at this point, for it was a fearful device, with some terrible trim rattles and very disappointing ride and handling. There's a chance that it may have been a pre-production model (that's still being checked) and I hope it was; if not, Ford has a widescreen quality control problem on its hands.(Update: Ford has confirmed that the first car I drove was indeed an early-build example.)Assuming that the second car was more representative, I'm impressed with the way the B-MAX drives. It feels a little top-heavy, because it is a little top-heavy, being nearly five inches taller than a Fiesta, but it handles well enough, and soaks up bumps in the road easily.The most annoying thing about it - and stop me if you've heard this before - is the stupid rear window design which makes it very hard to see what's immediately behind you in situations when that matters. Ford has assured the UK motoring press that it welcomes criticism of the car, so here goes: LARGER REAR WINDOWS NEXT TIME, PLEASE! Thank you.According to early forecasts, a quarter of the B-MAXes sold in this country are likely to have diesel engines, though Ford people believe this may be pessimistic. There are two diesel units in the range, the more powerful being the 94bhp 1.6-litre TDCi tested here. Oddly, it has better official fuel economy (70.6mpg) than the 74bhp 1.5-litre alternative (68.9mpg), though it is not necessarily to be expected that the two cars would be listed in that order in real life.CO2 emissions according to the EU test are 104g/km, a figure unmatched by anything else car in the class other than the petrol-electric Honda Jazz Hybrid.Much is being made of the one-litre EcoBoost petrol turbo version which is being offered in the B-MAX in 98bhp and 118bhp forms. It's widely hailed as a very fine unit, but the diesel is much less thirsty and gives perfectly adequate performance. Other than the extra initial cost, there's very little to be said against it.The only trim level available with the 1.6 diesel is the top-spec Titanium. As standard, this includes the SYNC system not previously offered on any Ford sold in Europe. An extension of the increasingly familiar connectivity between the car and phones or music devices, this award-winning set-up includes voice commands, reading aloud of text messages and the Emergency Assistance feature which lets you call local emergency services in the event of an accident. Engine 1560cc, 4 cylinders Power 94bhp Transmission 5-speed manual Fuel/CO2 70.6mpg / 104g/km Acceleration 0-62mph: 13.9 seconds Top speed 108mph Price £18,895 Details correct at publication date