Try your hardest to find a farmer or someone who has tractors and get them to let you come and visit, or better, bring one to your yard. Try farmers, local riding schools, riding clubs, anyone with a tractor or waggon and beg them to let you pay a visit! Trying to get your horse used to the if and when you come across one will take ages and won't be the safest or best plan. Showing big vehicles to your horse whilst they're not on will be a start so he gets used to the look of them without the scary engine noise. Just lead him slowly up to them and let him have a good look, find some grass or take a bit of food and wait til he has calmed down. Then walk away and try again another time. Let him find out for himself that they're not going to eat him. If he starts to panic then ease off the pressure and move him away til he calms again. End on a good note and make sure you lead him away rather than him drag you away. If the last thing he remembers is being scared of the tractor then it'll be harder to calm him the next time. Just slowly build up until he doesn't bat an eyelid and will happily walk up to and around them. Then you can progress onto getting him used to them whilst started up, using the same techniques.

If you hack alone find a friend or someone who can go out with you. your horse willsee theres nothing to be scared of also try walking with him next to the road and calm him down