Welwyn has some busy roads if you're not doing them late, I reckon.
Potters Bar has a few, but it's not the flattest. E4 has The Moletrap 15.3 miles into a 28.4 mile route which isn't quite halfway but given it's just before a descent I think that makes up for it... http://www.themoletrap.co.uk/Welcome.html
Welwyn has some busy roads if you're not doing them late, I reckon.
Potters Bar has a few, but it's not the flattest. E4 has The Moletrap 15.3 miles into a 28.4 mile route which isn't quite halfway but given it's just before a descent I think that makes up for it... http://www.themoletrap.co.uk/Welcome.html
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