A vehicle configured to operate in an autonomous driving mode, the vehicle comprising a tractor unit including: a driving system configured to perform driving operations in the autonomous driving mode; a fifth-wheel (110; 236) configured to detachably couple to a kingpin (108; 238) of a trailer, the fifth-wheel including a clamp mechanism and a connection surface, the clamp mechanism arranged to secure to a clamp section of the kingpin, the connection surface including a pneumatic connection section and an electrical connection section, wherein: the pneumatic connection section includes one or more slots (402,404; 412,414) arranged along the connection surface to align with one or more holes (316, 318) on a contact surface of the kingpin, the one or more slots being configured to provide air pressure to a braking system of the trailer, and the electrical connection section includes a set of electrical contacts configured for operative communication with an electrical contact interface of the kingpin; a perception system including one or more sensors configured to detect objects in an environment surrounding the vehicle, wherein the one or more sensors of the perception system includes at least one sensor positioned on the tractor unit to identify a relative position of the trailer to the tractor unit so that the fifth-wheel can be aligned to capture the kingpin; and a control system operatively coupled to the driving system, the perception system and the fifth-wheel, the control system having one or more computer processors configured to receive data from the perception system, to direct the driving system when operating in the autonomous driving mode based on the data received from the perception system, and to control communication with the trailer via the set of electrical contacts of the fifth-wheel. a driving system configured to perform driving operations in the autonomous driving mode; a fifth-wheel (110; 236) configured to detachably couple to a kingpin (108; 238) of a trailer, the fifth-wheel including a clamp mechanism and a connection surface, the clamp mechanism arranged to secure to a clamp section of the kingpin, the connection surface including a pneumatic connection section and an electrical connection section, wherein: the pneumatic connection section includes one or more slots (402,404; 412,414) arranged along the connection surface to align with one or more holes (316, 318) on a contact surface of the kingpin, the one or more slots being configured to provide air pressure to a braking system of the trailer, and the electrical connection section includes a set of electrical contacts configured for operative communication with an electrical contact interface of the kingpin; the pneumatic connection section includes one or more slots (402,404; 412,414) arranged along the connection surface to align with one or more holes (316, 318) on a contact surface of the kingpin, the one or more slots being configured to provide air pressure to a braking system of the trailer, and the electrical connection section includes a set of electrical contacts configured for operative communication with an electrical contact interface of the kingpin; a perception system including one or more sensors configured to detect objects in an environment surrounding the vehicle, wherein the one or more sensors of the perception system includes at least one sensor positioned on the tractor unit to identify a relative position of the trailer to the tractor unit so that the fifth-wheel can be aligned to capture the kingpin; and a control system operatively coupled to the driving system, the perception system and the fifth-wheel, the control system having one or more computer processors configured to receive data from the perception system, to direct the driving system when operating in the autonomous driving mode based on the data received from the perception system, and to control communication with the trailer via the set of electrical contacts of the fifth-wheel.