From the seventeenth century, coal had been extracted in the area north of the River Tyne, at first close to the river to allow onwards transport by boat. As the easiest deposits close to the river became worked out, the focus of mining was pushed back further, and transport to the waterway was essential. Wooden waggonways were introduced and were relatively successful, but a major limitation was the issue of "wayleaves", by which owners of land on the proposed route could demand payment, usually on a tonnage basis, for allowing the passage of the wagons. The wayleave demands were heavy, and this continued to be a major difficulty.