Other people will be more knowledgeable than I am, but I've parked in a little lot on Quaker Road at 40.3085, -74.6804. The Canal tow trail runs RIGHT by there, and you can do a ten-mile out and back N/NE and only cross three roads. You can also run on the path along Quaker Road into the Institute woods and then into Princeton.
Several lots. The D&R Canal website lists coordinates for several in the Princeton area.
Thanks! Your answer is awaiting moderation.