The introduction of the new car tests, the WLTP and RDE tests, marks an important milestone in the battle to ensure cars comply with environmental limits on the road and to end the cheating that has become endemic in emissions testing. But, as this briefing outlines, new tests are not a panacea and will need to be further refined to ensure they are really representative of how cars are driven. The forthcoming decisions on how and who approves cars for sale will be key to ensuring the system of approvals is independent and rigorously enforced.