Reducing harmful emissions from London’s iconic bus fleet has also become a key campaign issue. Labour candidate Sadiq Khan and Liberal Democrat candidate Carol Pidgeon, as well as Goldsmith, all say they will ensure that the city only adds clean energy vehicles to its bus fleet, though they vary on some of the specifics, according to a report from U.K. think tank Policy Exchange. “Whoever is elected, there is definitely going to be some change and accelerated action on this issue,” says Richard Howard, head of environment and energy at Policy Exchange. “There is a desire to tackle the problem that maybe wasn’t there in the past.”