True multi-modal travel is now commonplace. Car, bus, train, bike, walk are all compatible with the advent of lightweight fast-folding lightweight folding bicycles. They used to be so few and far between that owners would wave to one another in passing but within just a few years folders have moved beyond niche, through trendy and into general utility.

Bikes are great when they're carrying you along, but when the roles are reversed they can be nothing but trouble. Whether you're trying to get on a train or just into your cramped apartment, their famous efficiency can seem small compensation for the trouble they can give, especially when short-sighted architects and train operators get in on the conspiracy. Which is a great shame, as the bike is the undisputed king of the short-distance journey, and so should be ideal for people living in densely-populated areas. And what more efficient way of long-distance travelling can there be than combining rail and bike? But sadly, it is rarely easy getting a standard bike on a train, especially at peak times.

So, how about a bike you can fold up and put in a bag? Sounds ideal, but what's it like when you put it together again and ride off into the traffic? The first modern folders were clunky heavyweights designed to be plonked into in the boots of cars rather than carried any distance to public transport. They were folding utility machines, shopper bikes which could be built cheaply, used occasionally and dumped in the shed when their performance quickly sapped the initial enthusiasm of the owner. It was the desire to design bicycles which could be carried some distance and over a station platform bridge without rendering the owner incapable of cycling which led to some extraordinary advances. Some models fold small enough to be taken on planes as hand-luggage.

There is usually an area of compromise, between foldability and rideability, and so the best folders are, of course, those which do both well. There is huge variety. Some models need a minute or two to fold down, others fold in seconds. Some are great for round-town, others you could race on. Some have small wheels combined with suspension, others are just standard bikes which fold in the middle. You have to set your own priorities, which might include comfort, handling, weight, ease and speed of folding, size when folded, and of course, cost. The challenge of meeting these needs has fascinated many an experienced designer.

Many folders are bought by practically-minded people who would run away from the notion of 'cycling as lifestyle'. At the other extreme are folder enthusiasts have developed their own sub-culture, clubs and events. Owners' motivations may vary, but there's little can beat the sheer practicality of jumping off a train and onto your unfolded bike, as fellow travellers queue for taxis and buses.