As political u-turns go, Ken Livingstone’s boisterous claim in 2001 that only a “ghastly dehumanised moron” would get rid of the famous London Routemaster bus ranks up there with, well, our new coalition government. His successor has been desperate to avoid a similar policy pitfall which is one reason why Boris Johnson appeared little short of euphoric earlier this week when he unveiled long-awaited designs for the new Routemaster bus – a key pledge of his election manifesto.

Designed by Heatherwick Studios and Wrightbus, the new bus looks like an old Routemaster that has been manicured, plucked and polished to within an inch of its life. The projecting driver’s cabin and wind-down openable windows of the old model have gone and the engine has been moved from front to back. But the iconic open-rear platform has been retained (albeit in a slightly altered format) as have the inset wheels, simple lines and curvaceous roof that made the old Routemasters such distinctive, architectural classics.

It is to the designers’ credit that the new bus appears so similar to its predecessor while making such extensive concessions to modernity. However, not all these concessions are necessarily successful. The lack of articulation between windows and wall gives the vehicle a hermetically sealed look that suffers heavily in comparison to the textured elevations of the old buses. There appears to be no rear window to the upper deck. And the asymmetrical, diagonal ‘swoops’ applied to the front and back seem a touch contrived and over-zealous.

But new elements such as its hybrid diesel/electric plant which uses 40% less fuel than current models promise sizable environmental benefits. Aesthetically, the sloping row of side windows that picks up the internal staircase will also allow much more natural light into the interior and will help the bus establish a strong and unique new visual identity within London’s hectic streetscape.

Internally, the new bus is perhaps more controversial. Strangely, it will have two staircases. As well as appearing ludicrously inefficient, the front staircase apparently necessitates the removal of the front rows of seats on the upper deck. As several Londoners and any tourist will attest, sitting upstairs at the front of a London bus is one of the unmitigated cosmopolitan joys of this city and its removal seems churlish and inept.

Presumably, the offending additional staircase is also partially responsible for the bus’s relatively unimpressive passenger capacity. Despite being almost 3m longer than the old Routemasters, it has two less seats than its predecessor and only carries around the same number of total passengers (87) as current double-deckers models. (Those detractors keen to point out that it holds just over half the capacity of the bendy-bus would do well to remember that the latter takes up almost twice as much road space and has far fewer seats.)

Admittedly, the current accessibility and disability requirements that the new bus has invariably (and rightly) had to adhere to have in all likelihood encroached upon the number of seats provided. Yet one would still have expected the layout design to respond more efficiently and imaginatively than it would appear to have done.

The bus’s three doors are also a controversial and unexpected feature, particularly when multiple unmonitored entrances shoulder much of the blame for the fare evasion epidemic that blights the bendy-bus. The rear entrance will be a shuttered hybrid of the old Routemaster’s much missed open platforms, marking the welcome return of one of their most popular and effective design features.

But worryingly, Transport for London claims that they will only be used when the buses are manned by secondary “uniformed” personnel at select times. Exactly what this means is anyone’s guess. However, as there has been no explicit TfL commitment to the reinstatement of conductors, uniformed personnel could potentially refer to anyone from traffic wardens to schoolchildren. Neither group offers much prospect of the platform ever being in frequent use. All of which points to an overly complicated operational strategy potentially open to exploitation, mismanagement and misuse by customers and operators alike.

Although costs are expected to drop to £300,000 per vehicle when production increases, (Boris wants “hundreds”) the initial cost of the first five models will be an eye-popping £7.8m. In addition, the new buses are not expected to make an appearance on London’s streets until 2012. It is not surprising therefore that the proposals have attracted stern criticism from some corners, particularly in these times of severe economic constraint. But, with the greatest respect, these fiscal naysayers have missed the point.

Yes the price tag is riotously expensive. But so was Ken Livingstone’s unnecessary replacement five years ago of the entire fleet of recently modernised Routemasters with new bendy-buses patently unsuited to London’s roads. But more importantly, what Ken and his TfL henchmen failed to realise is that the red London bus isn’t just a proprietary metal cage carrying as many people across the city as possible by any means necessary.

It is an intrinsic part of London’s urban streetscape and civic identity, woven into our cultural fabric and collective consciousness as deeply as Big Ben, garden squares and pint glasses. In an age where the term ‘iconic’ is banded around like confetti, they prove that iconic status is more often attained by what an object represents rather than what it is.

Is London Bridge iconic because its current incarnation resembles a motorway flyover or because of its historic associations and an old nursery rhyme? The same thread of emblematic symbolism applies to the red double-decker London bus whether it is a Routemaster or not.

Therefore, harnessing design to restore the status of one our most conspicuous and recognisable urban accessories – however prosaic and unglamorous buses may seem – proudly articulates our civic priorities to the outside world. It also helps project an indelible image of how we see ourselves as a city and how we wish to be seen by others. Consequently, this new bus is as crucial to London’s urban branding and public infrastructure as the Olympics yet comes at only a fraction of the cost.

Furthermore, by following the Routemaster tradition of having a bus designed exclusively for London, it promises to further enrich the prestige of the capital’s public realm. It will also have the potential to reflect and enliven London’s cityscape in a way the impoverished, anodyne aesthetics of the bendy-bus never could. Finally, it represents the kind of pioneering, visionary municipal ambition that was once the hallmark of London local government under the lauded stewardship of the London County Council. In so doing, it potentially offers a rare concentration of civic pride and political will.

For all these reasons, London’s new bus is not only important but worthwhile. And hard as it may be to contemplate in these frugal times, it is its value that will leave the longest legacy and not its cost.