For as long as there have been cities, there has been traffic congestion. And for almost just as long, people have been looking for ways to use technology to solve it. Technological innovations from the lowly traffic light to electronic real-time congestion tolling have been installed by cities to try and tame congestion through the years. Most recently, plans to equip vehicles and roads with sophisticated electronics that allow them to communicate with each other – dubbed ITS or intelligent transportation systems – are poised to provide more help to motorists trying to avoid continually worsening traffic jams (often by taking control away from the motorist).

Most of these solutions require large investments upon the part of governments and vehicle owners – and are decades from widespread adoption. New web-enabled GPS navigational devices will soon be able to provide commuters with advice for avoiding traffic snarls. But for cities and commuters looking for help immediately, one new media technology offers a compelling solution – Twitter.

In case you don’t know what it is, Twitter is a free web service that allows people to publish short messages on the web and subscribe to receive messages published by others. Limited to 140 characters – so they can do double duty as SMS text messages – Twitter messages, or “tweets”, are perfect for sharing bite-sized bits of real-time information – say, like traffic alerts. Since tweets can be categorized using keywords known as “hashtags” – so called because they begin with a hash mark – the service makes it easy for people to filter through the millions of messages posted daily. And with about 15 million active users – there’s plenty of people willing to serve as scouts for traffic problems.

In Caracas, the traffic-choked capital of Venezuela – almost 20,000 people subscribe to receive updates from Traffico – the city’s unofficial traffic twitter feed. Thousands more subscribe to other competing feeds. On the other side of the world, software maker SAP designed an iPhone application that analyzes tagged tweets to display traffic incidents in Sydney and Brisbane, Australia on a digital map.

Here in the U.S., a free service called Commuter Feed offers traffic updates gleaned from twitter users for 10 large metro areas – including Houston, Washington, D.C., and Los Angeles. Taking the idea one step further, developers involved with the DIY City project experimented broadcasting real-time traffic reports from commercial services such as Yahoo using Twitter.

Of course, traffic itself isn’t the only thing that Twitter can be used for. In New York City, where officials held a contest for developers to make use of the City’s recently released data, a team of developers create Taxihack.com – a website that collects data about the City’s taxi fleet from tweets. New Yorkers who want to comment on a recent cab ride experience can send a message to the site’s twitter account (in this case, @taxihack) with the cab’s medallion number, and the site automatically displays all the messages online, while compiling reports on certain drivers and companies. Transit agencies are also beginning to use Twitter to alert riders of service delays.

In all of these examples, no new infrastructure or administration was needed to create these tools, and in most cases, local government wasn’t even involved. This is just another example showing when citizens and web developers get together to rethink how cities can work better using new media, the benefits can be extraordinary.