Instructions
Load "GMod" and open the spawn menu by hitting "Q," selecting the "Props" tab and choosing "Hl2: Characters," which will bring up a list of ragdolls. Select a ragdoll to spawn in the game.
Open the spawn menu again and select to spawn a body for the vehicle, such as a box, gas tank or anything else about the size of the ragdoll.
Lift the object a little off the ground with the physics gun and freeze it there.
Open the spawn menu again and click on the "Tools" menu on the right, and select "Wheels" under the "Construction" category. Select the type of wheel to use for your vehicle.
Place wheels on opposite sides of the object you spawned in step two and weld them onto it.
Open the spawn menu again and select "Rubber" under the "Properties" options. Shoot the wheels to make their properties rubber.
Select "Keep Upright" under the "Tools" menu and shoot the vehicle to ensure that it stays upright while moving.
Select the "No Collide" property from the "Tools" menu and shoot all parts of the vehicle to allow objects to pass through it.
Pick up the ragdoll with the physics gun and position it next to the vehicle. Freeze the torso of the doll in place and move each foot onto a wheel. Weld the ragdoll's feet to the wheels. Weld the torso to the body of the vehicle.
Drop the vehicle back down to the ground and open the spawn menu again. Select the "Color" option under the "Render" category in the "Tools" menu and choose to reduce the the opacity as much as possible so that the vehicle becomes transparent.
Apply the clear color to all parts of the vehicle so that it is invisible.
Make the vehicle move and it will appear as though the ragdoll is walking.