I use a dog trailer like the one that Gary E links to for my Westie, and he gets on fine in it. He's fidgety at first, but soon settles down. Different kettle of fish to your lab of course, as my little mutt is only 8kg. To attach the trailer there is a pin that fits under the rear wheel nut on the left hand side. This is the only part that is permanently fitted to the bike. The trailer hook-up attaches to this pin, secured in place with a retaining clip. Rigmarole is assemble trailer, install dog, attach trailer to bike, mount bike and ride. It's easier with someone to help of course, but can be done single handed.