how to stop toodler from dashing

hi mummies. my son is in love with bus. everytime he see a bus, he always wanted to dash to it. but its too dangerous. everytime is a tug of war trying to stop my baby from running towards a moving bus. or crossing the rd, i will always hold my sons hand tightly. i'm a small size mum and my son is damn too heavy for me to carry all the time or when i have stuff with me. can i ask how do your teach your kids not to run towards moving cars? or anyways to encourage not to?