Complex sentence: The first two tunnels were replaced by Woodhead 3, which was longer than the other two at 3 miles 66 yards (4860m), which was bored purposely for the overhead electrification of the route and completed in 1953.
Split into simpler sentences: The first two tunnels were replaced by Woodhead 3, which was longer than the other two at 3 miles 66 yards (4860m). It was bored purposely for the overhead electrification of the route and completed in 1953.