Zwift Meet Up Start Locations

I created my first zwift meet up yesterday, selecting the London Greater Flat route as none of the participants had completed the achievement badge for this route yet. The meet up started on the wrong side of the barrier however so one lap didn’t result in the achievement unlocking.

Is there any map showing where each of the route meet-ups start? If not is there any guaranteed method of unlocking route badges without having to do an extra lap?