George Bernard Shaw once said that England and America are two countries separated by a common language, a comment that is also true for car crash-test assessments. Much has been made in the United States of a report from the Insurance Institute for Highway Safety (IIHS) which rated the BMW 5 Series as the worst for side-impact crash protection in the luxury sedan group, giving it a rating of "marginal" although this was a relatively small test of 12 cars, three of which were not tested for side-impact ratings.

Most of us, when we buy new cars in Britain and, in fact, across Europe, are familiar with the term "Euro NCAP rating", a mark, out of five stars, that has been accepted as the standard for safety ratings. Of course, these are not in-depth, totally comprehensive crash tests of every car on the market, as manufacturers are expected to conduct these themselves. They are, however, "a realistic and independent assessment of the safety performance of some of the most popular cars sold in Europe", according to Euro NCAP, which is also known as the European New Car Assessment Programme.

It has been in existence now for 10 years, providing motoring consumers - that's both you and me and car manufacturers - with a standard by which we may judge a car's safety. It has got some weight behind it, too - Euro NCAP is backed by five European Governments and the European Commission, as well as motoring and consumer organisations in every EU country. When it was first conceived, manufacturers shunned it, but the programme gained acceptance once it was seen to be technically correct - not forgetting, of course, that cars which received good ratings saw an increase in sales figures and those that did badly saw a decrease.

So do British 5 Series drivers need to be worried about the IIHS's report? Well no, probably not. The 5 Series right-hand drive model on sale in this country gets a four-star rating on the Euro NCAP, in which the side-impact tests actually rated as the strongest part of the car. A spokesman for BMW GB said: "These results were specific to US road conditions that spotlight US vehicles such as trucks and large pick-ups. Of far more relevance to British drivers is that the BMW 5 Series has been rated highly in the EuroNCAP testing process, with strong ratings for both front driver, front passenger and, in actual fact, an even stronger rating for side impact."

He is right - the two tests cannot be compared as the IIHS's side-impact tests for the States now use a pick-up sized object as the standard for assessing a side-impact crash, because of the enormous growth in popularity of these and SUV-type vehicles, whereas you are far more likely to be t-boned by an ordinary saloon in the UK.

Tests differ, too, even between NCAP partners. In the European side-impact test, for example, only 40 per cent of the vehicle width is impacted into a deformable barrier face, whereas in the United States - yes, just to confuse the issue, there is a federal NCAP there and the IIHS, as the name suggests, is an independent organisation which is wholly supported by insurance companies - the entire width is impacted into a flat, rigid wall. Euro NCAP say that their test is more representative of on-road accidents and therefore provides a more stringent test of the vehicle’s structural integrity and rigidity.

It is not all them and us and never the twain shall meet, however. The Volvo S80 is a Top Safety Pick with the IIHS and also gets four stars from Euro NCAP, while the Audi A6 gets a similarly good rating in the States and five stars in Europe. But if you want an example of just how far apart the two countries can be, check out the contrasting frontal impact tests of the Kia Sedona from both Euro NCAP and US NCAP here.

Indeed, we are two countries separated by a common language, not to mention several stars on a safety rating.