From your second link:
&gt;&gt;&gt;The junction provides access to and from the A38 (Tyburn Road), A38(M) (Aston Expressway), the A5127 (Lichfield Road&#x2F;Gravelly Hill), and several unclassified local roads. It covers 30 acres (12 ha), serves 18 routes and includes 4 km (2.5 mi) of slip roads, but only 1 km (0.6 mi) of the M6 itself. Across 5 different levels, it has 559 concrete columns, reaching up to 24.4 m (80 ft). The engineers had to elevate 21.7 km (13.5 mi) of motorway to accommodate two railway lines, three canals, and two rivers.<p>Truly an inspiration to those of us who grew up with Erector Sets and Tinker Toys.