Complex sentence: Then a turnpike was opened on a new route that is still today's A40, with upwards of 80 coaches making the trip to London daily; a turnpike milestone from this era can still be seen near the Thornhill Park and Ride.
Split into simpler sentences: Then a turnpike was opened, with upwards of 80 coaches making the trip to London daily. Today, a turnpike milestone from this era can be seen near the Thornhill Park and Ride.