Rather than ask all these questions, you can simply download a cut down version of our software from the website and have a play with it. The database only has the Warrington areas but it's more or less fully functional. Quite a few small companies do this and modify the tables (MS Access) to work for their own area and because we don't charge for the software, we really don't mind anyone doing this. You probably will have to change the date format to use the short date (dd/mm/yy) for it to work. Log in as demo for the user and demo for the password.
It's taken over seventeen years to develop this code with two full time programmers and yet, on our own internal forum, we still get literally hundreds of requests for minor code changes and tweeks. Some say "you must have crap programmers then if it takes that long" but that simply illustrates the level of lack of understanding as to what constitutes a basic taxi dispatching system. Fresh out of university, our two estimated it should take no longer than six weeks to write the code but seventeen years down the line and they're still here working long hours and with hair turning ever more grey.
Writing code can be challenging and fun if you're that way inclined but if you want to turn it into a commercial venture then bear in mind you're taking on board the responsibility for the livelihoods of everyone that uses it. If it breaks then people don't earn money. If they don't earn money, they leave the company.
Bill