Simplify the following text for a Grade 7 native English-speaking person.
Original: The main route from Fenchurch Street to Shoeburyness via Basildon is 40 m long , and the fastest timetabled journey time from Fenchurch Street to Shoeburyness is 58 minutes .
Simplified: The main route from Fenchurch Street to Shoeburyness via Basildon is 39.5 mph and the fastest timetabled journey time from Fenchurch Street to Shoeburyness is 58mph giving an average speed of 40.7 mph , although the route can be done in 47mph , giving an average speed of 50mph .