When Nedry was heading for the dock

So he drives his Jeep Wrangler to a place where he can see a signpost for the dock, but it's high up and the road is lower down. So why does he need to painstakingly pull out the winch cable to wrap it around a tree on the road lower down? Surely he would achieve the same thing, even better, by just driving the Jeep down the slope?

Honestly, I've never understood this scene. It's almost up there with the sheer drop on the other side of the electric fence even though the T-Rex was walking by it earlier!