We had vole holes all the way down the side of the driveway the last 7 years or so. We called an exterminator for a quote a few years ago. They could set out traps to catch the odd one, but said the most effective way they had was constant monitoring and resetting traps every few weeks, which they would not guarantee and was quoted at about $600 or so if I remember correctly.
Some things I've heard that work are the poles that send pulses into the soil and disturbs them.
Apparently a dog running around does the trick as well.
We had a relatively vole free season this year. Part of it is my son is old enough to play for hours outside now, which we did, which may have had the same effect as the last 2 points.
The guy who cuts our lawn approached us to test an idea he had and tried. They dug a little trench, put in some gravel and bricks. The voles apparently hate that stuff. So we have it a shot - worst case scenario, we have a decorative piece by the drive way with some vole holes. It's been about a year, and they haven't dug by the driveway at all (but seem to be in the flower beds, which is not a big deal for us).