will raised bed be ok on tarmac

Have you thought about drainage? Also, worms can't get through tarmac and you need them when you dig manure and compost in, so all in all, I'd say it's not a good idea, Mazooma.

Yes, I definitely agree with Spritz, a solid surface is not suitable for a raised bed. If you take off the tarmac, underneath is rubble which should be good drainage. Cover rubble with a sheet of thick plastic, making holes in it before adding soil/compost.

Check out the book (or website) by Mel Bartholomew called Square Foot Gardening. He explains how to make and maintain a raised style bed on an alternative base. If tarmac is all you have it can be done, it just takes a different approach. I have been doing it for 2 years. "Sleepers" are what we in the US call railroad ties and are heavily treated against insect infestation and the pesticide can leach into the soil so might not be good for vegs.

Remember the depth of veg you are wishing to grow and cater for that.
Worms are no problem if you add some, just add some when you add your soil, compost, manure etc.
I think your main problem will be retaining water so add lots of organic material, keep an eye on your raised bed/s, remember to add the correct organic material for the specific veg in your rotation system.
Good luck