It's increasingly common for new cars to be provided with a tyre repair kit rather than a spare wheel. This is mainly due to manufacturers doing everything in their power to reduce CO2 emissions – a typical 17-inch alloy wheel weighs about 20kg, which can add up to nine grams of CO2 to an average vehicle’s emissions. There are also packaging reasons – many modern hybrid vehicles have batteries under the boot floor, meaning there's less space to fit a spare wheel. And, inevitably, there'll be an element of cost-cutting – a tyre repair kit will be cheaper than a spare wheel.