The key services were numbered 1 to 8, and ran every 10 to 20 minutes. Key services ran through the busiest parts of the city, for example to Bletchley and the District centres. Intermediate services ran from every 20 minutes up to every hour. These routes cover areas in more detail, for example serving through the grid squares, while key services mostly ran on the main roads. The other routes ran at a frequency of every hour or less. These services linked locations outside Milton Keynes into the city, or linked neighbourhoods into the nearest centre.