Twenty miles an hour 'homezones' are an important contributor to road safety, according to the Network Planning Manager for the Department of Transport.
In the United Kingdom there are plans to design new towns around an even lower 15mph limit, primarily to force people out of cars as part of an effort to reduce global warming.
A number of organisations have complained that traffic-calming measures, such as speed bumps and width restrictions, are actually counter-productive.
It's also claimed they can be dangerous, especially if they impede the progress of emergency service vehicles like fire appliances and ambulances.
But Derek Sewell (pictured) says it's not just the Department of Transport that wants lower limits in built-up areas:
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