Answer:
The city planners accomplished the building of such a trail in a heavily developed urban area as the trail was formerly a railroad line.
Explanation:
- The city planners actually did not separately build a running and bike trail but just transformed the old railroad line that was not in use anymore to make it a running and bike trail.
- The city planners must have got the idea of its transformation into a bike trail while thinking for an alternative to the demolishment or uprooting of the railway track.