Find somewhere you can ride at a constant high speed with no interruptions for long periods of time and chuck in some 100-200m sprints every so often.
A track is very actually the best place to do this but you might be able to find a circuit you can work with. I was doing lots of 50+ mile rides fixed and thought they would be good prep for pitching up at Herne Hill but it really is something else entirely.
Find somewhere you can ride at a constant high speed with no interruptions for long periods of time and chuck in some 100-200m sprints every so often.
A track is very actually the best place to do this but you might be able to find a circuit you can work with. I was doing lots of 50+ mile rides fixed and thought they would be good prep for pitching up at Herne Hill but it really is something else entirely.