I have a database of some 60K entries, and I want to restrict the records returned to those within a drivetime zone.

I initially just exported the zip codes in the drivetime zones, BUT... It only includes the zips whose CENTROIDS are within the drivetime zone, but if the centroid of the zip code is not in the drivetime zone then the zip is left out. SO...

I'm now restricting the database records to the counties that might encroach the drivetime zone. Then, I perform a DistanceTo() operation on the record (from the center of the former drivetime zone), and test to see if within a mileage limit. Finally, I perform a Calculate() on the record to see if it's within the driving time I want to limit. If so, I flag the record in the database that it's within the prescribed time.

However, this process is fairly time consuming/processor intensive.

Any optimization thoughts?