RoRo ships, short for roll-on/roll-off ships, are designed to carry wheeled cargo that can be driven onto and off the vessel. Car carriers are a specialized type of RoRo ship built to transport thousands of cars, vans, trucks, buses, and heavy machines across oceans. They matter because they make vehicle transport faster, safer, and more efficient than lifting each vehicle by crane.
Their tall, boxlike shape hides a complex system of ramps, decks, lanes, and securing equipment.
Key Facts
- RoRo means roll-on/roll-off, where wheeled cargo enters and exits by ramps instead of cranes.
- Average density matters for floating: density = mass / volume.
- A ship floats when buoyant force equals its weight: F_b = W.
- Buoyant force is the weight of displaced water: F_b = rho_water g V_displaced.
- Cargo capacity is limited by weight, deck area, deck strength, and stability, not just by empty space.
- Vehicle decks use lashings, wheel chocks, ventilation, and fire detection systems to keep cargo safe during a voyage.
Vocabulary
- RoRo ship
- A roll-on/roll-off ship is a vessel designed so wheeled cargo can be driven aboard and driven off using ramps.
- Car carrier
- A car carrier is a RoRo ship specialized for transporting large numbers of cars and other road vehicles.
- Ramp
- A ramp is an inclined loading structure that connects the ship to a dock or one deck to another deck.
- Vehicle deck
- A vehicle deck is an internal level of a RoRo ship where cars, trucks, buses, or machinery are parked and secured.
- Lashing
- A lashing is a strap, chain, or cable used to tie cargo down so it does not move during waves, turns, or braking.
Common Mistakes to Avoid
- Thinking RoRo ships lift all vehicles by crane is wrong because the main advantage of RoRo design is that cargo is driven on and off through ramps.
- Ignoring ship stability is wrong because loading too much weight high in the ship can raise the center of mass and make the vessel less stable.
- Assuming every deck can hold any vehicle is wrong because each deck has limits for height, weight, axle load, and turning space.
- Forgetting to secure parked vehicles is wrong because waves and ship motion can make unlashed cargo roll, slide, or collide with other vehicles.
Practice Questions
- 1 A car carrier loads 4,800 cars with an average mass of 1,500 kg each. What is the total mass of the cars in kilograms and metric tons?
- 2 A RoRo ramp rises 4.0 m over a horizontal distance of 20.0 m. What is the ramp slope as a percent, using slope percent = rise / run x 100?
- 3 Explain why a car carrier needs internal ramps and carefully marked lanes instead of simply using one large open cargo space.