Most people's first sight of a museum is the sign that points to it. And in most cases in Britain, it's the brown sign with the standard museum symbol - a capital M, raised on a podium, imprisoned in a box, and topped by a portico. Whenever I see that road sign, my heart sinks.

The symbol is, of course, only a symbol, and the reality of most museums is very different. Yet the sign does reflect the ideas that most people have in their heads when you say the word "museum": somewhere formal, traditional, proper and slightly intimidating. The symbol says something about the museum brand - and it's a brand that needs to change.

We all know that individual museums have built big brands. At June's Communicating the Museum conference in Venice, I surveyed the delegates on their views on museum branding.

More than 100 responded and a clear view emerged of the top five museum brands: Tate (63 mentions), MOMA (23), V&A (19), Louvre (13) and Guggenheim (11).

These museums know that to build a brand, you need to stand for something: a clear idea that's expressed through your collection, your public programmes, your buildings - indeed, everything you do. And brands such as Tate have changed not just the way people feel about the institution, but also the way they think about art.

But the idea of the museum as a whole hasn't changed. Many people still see museums as closed, institutional, boring: essentially 19th-century institutions that are about dead objects and that are "good for us" rather than "ours". And that symbol serves subliminally to prove the point.

The truth, of course, is not so simple. Many museums are idea-led. They ask audiences to take part. They collaborate; they invite outsiders to curate shows; they recognise that, in the web 2.0 world, people are less receptive to a dogmatic, one-way kind of authority - particularly an authority whose voice is narrowly western and middle-class.

You only have to think of participative public programmes such as Tate's Long Weekend or the World Beach Project at the V&A. Or exciting collaborations like History Matters. Or the National Trust touching completely new audiences through projects such as the Untold Story.

My Venice survey showed these kinds of changes are happening worldwide. For example, 61 per cent of those surveyed say they want visitors to become more like participants.

Over 70 per cent are ramping up their online activity, and 71 per cent are collaborating more. In the UK, 44 per cent want to become less authoritarian and 67 per cent want to be more cross-cultural.

So change is happening. But museums, being cautious, modest and slightly introverted things, haven't told the world about this. Now it's time to talk and think and look different: to show that museums have changed, and to stimulate further change.

The world is facing unprecedented problems of climate change, ideological conflict and diminishing resources, and needs new thinking more than ever. And it needs thinking that's grounded in reality - in real objects, real documents, real buildings, real works of art.

It needs thinking that's collaborative, that builds on different cultural perspectives, but that's also serious and rigorous. And it needs beauty, peace, calm, a different rhythm from the mechanistic, email-regimented lives that most of us now live. All of which museums can provide.

Somewhere here is the starting point for building a brand for museums as a whole - an idea not of what museums do, but of why they matter. Not a remit or mission, but a purpose or cause.

This new age is scary in some ways, as museums establish a new kind of authority. Not so much the oracle, more the provoker and organiser of ideas. Less the single-minded, all-knowing author, more the subtle and collaborative steering of the editors behind Wikipedia. If museums can embrace this, they will attract new kinds of visitors, and new kinds of public and private support.

This isn't about dropping the word "museum" in embarrassment. It's about updating the meaning of the word, creating a new and exciting idea that museums in general can stand for.

It's also about using that idea to change both the image and the reality of museums - using the surprising things that some museums are already doing to get people to change their minds about museums in general, and to provoke more museums to do yet more surprising new things.

We live in a sceptical age that believes reality more than image, so creating this new museum brand is much more about demonstrating change than talking about it.

And then finally, we must get that road sign redesigned.

Robert Jones is a consultant at branding consultancy Wolff Olins
Links

www.communicatingthemuseum.com