After Meredith asked whether Bruce Wayne was going to show up in Smallville, certain commenters wondered just how long a trip that would be. That's not the easiest question to answer, considering the entirely fictional nature of both Gotham City and Superman's hometown. Not that that's going to stop us taking a stab at answering it anyway... To the Bat-Atlas!
The real problem in working out this particular problem is the fact that these cities have a tendency to... well, to move. The Metropolis you see in Smallville seems to be within reasonable driving distance of Smallville, which would mean that it's somewhere in Kansas. But Metropolis in the DC Comics has always been a stand-in for New York, and - according to the Atlas of the DC Universe, created for DC's late '80s, early '90s role playing game - exists on the coast of New Jersey... right next to Batman's Gotham City, which is also a stand-in for New York City.
If you don't live in NYC, don't worry; DC has stand-ins for many real life cities throughout the world, not just America. In fact, when Marvel Comics' superheroes came to the DC Earth in 2003's JLA/Avengers series, the heroes from the (slightly) more-realistic Marvel Universe noticed that DC's Earth was actually slightly larger than their Earth because of all the extra locations... Locations like California's Coast City (home to Green Lantern), Indiana's Fawcett City (The original Question's stomping grounds), Missouri's Central City (where the Flash tends to spend his time) and Louisiana's Belle Reve, where the Suicide Squad relaxed between missions.
To get back to the original question, though, how long would it take for Batman to get to Smallville? It's a trick question; he'd just teleport there in no time using the Justice League Teleporter, of course.