In contrast, cars and light vans have increased every year and motorcycles and HGVs have increased since 2012 up to 2019.
Ar y llaw arall, mae nifer y ceir a faniau ysgafn wedi cynyddu bob blwyddyn ac mae beiciau modur a cherbydau nwyddau trwm wedi cynyddu ers 2012 hyd at 2019.