zone. that's not because nottingham is a dirty city. quite the opposite. its buses run on bio—gas created from food and farm waste. it has a fleet of zero emission electric taxis, an electric tram network, and has already reconfigured the roads to encourage fewer cars to drive into the centre and persuade more people to take public transport. we've been on a path towards cleaner airfor a long time. we implemented some anti—congestion measures. for example, we introduced the workplace parking levy, which was a charge on parking spaces at workplaces. it's helped us to develop a really integrated public transport system, which is very popular with people, and therefore, they're less likely to bring their car into work. which goes to show that there are lots of different ways