THINKING > TECHNICAL > TRAJECTORY

Trajectory

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A vehicle’s path through a curve is not just a result of turning the wheel, it is the product of motion, momentum, and precise control. Whether you are navigating winding roads, avoiding an obstacle, or steering through an intersection, your car’s trajectory determines how safely and accurately you stay on course. Understanding this concept is essential for improving handling, preventing accidents, and staying in control when conditions suddenly change.

What is a vehicle’s trajectory and how is it shaped by the road and your actions? How does your speed affect the direction your car takes when cornering? Why do some cars drift wide in turns while others cut too sharply? What influence does road slope or surface have on trajectory? What role does steering input play in maintaining the correct path? How does anticipating trajectory help you avoid collisions? What happens when traction is lost mid-turn?

This page breaks down trajectory in simple, practical terms, showing how steering, speed, road design, and traction all interact to determine your car’s movement. It also explains how understanding your trajectory helps you respond more confidently in emergency situations and navigate turns with greater control. Whether you're managing a sudden swerve or preparing for a sharp bend, knowing how your vehicle behaves through motion gives you a clear advantage behind the wheel.

Awareness of how other vehicles move, especially large ones like buses and trucks, can be just as important. Their size and turning patterns create unique challenges for nearby drivers.

What happens when a bus turns and its rear wheels follow a different path than the front? How does the rear overhang of a truck affect its movement in a tight corner? Why is it critical to recognize these patterns before you position yourself near them in traffic?

This page also explores how reading the trajectory of surrounding vehicles can help you avoid blind spots, anticipate motion, and make safer driving choices. From understanding how a long trailer cuts across lanes to recognizing where a large vehicle might swing wide, mastering these patterns helps you stay alert and better prepared for the movement of others on the road.

The trajectory is the path that an object, or point on that object, takes on its travel.

For our purposes, we are going to look at two trajectories that can affect us on the road, as explained in more detail in the accompanying video:

• ⮟ Inner

• ⮟ Outer

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🛈 Info:

• ⮟ Factors affecting the trajectory of a vehicle.

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Inner

• When a vehicle of considerable length (happens with any length vehicle, but more pronounced the longer the vehicle is) turns a corner, the body of the vehicle encroaches more and more into the inner space of the arc, so that the rear wheels land up cutting the corner with a much smaller radius.

• We (either driver or another road user) need to be aware of this so that we can give a wide enough berth to accommodate for the ever decreasing turning circle.

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Outer

• When a vehicle has a longish overhang (distance from the rear wheels to the back of the vehicle, or load that it is carrying), then when that vehicle turns a corner, the very rear point will swing outwards in a wider arc than the rear tires.

• The wider arc of the backmost point of the vehicle could easily catch or scrape any object in its path or even worse, injure a road user or pedestrian.

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🛈 Factors affecting the trajectory of a vehicle

The trajectory of a vehicle refers to the path it follows through space. Several factors can affect the trajectory of a vehicle, including:

• Velocity of the vehicle: The higher the velocity of the vehicle, the more difficult it is to maintain control of the vehicle, and the more prone it is to deviating from its intended trajectory.

• Vehicle weight: The weight of the vehicle can also affect its trajectory. Heavier vehicles are more difficult to control and can deviate from their intended trajectory more easily than lighter vehicles.

• Road conditions: The condition of the road, including the type of surface, level of traction, and the presence of obstacles or other vehicles, can affect the trajectory of a vehicle. Slippery roads, for example, can cause a vehicle to deviate from its intended path.

• Steering and suspension: The condition of the steering and suspension system can also affect the trajectory of a vehicle. If these systems are not working properly, the vehicle may not be able to maintain its intended path.

• Driver behavior: The behavior of the driver can also affect the trajectory of the vehicle. Distracted or impaired driving, aggressive driving, or other reckless behaviors can cause a driver to lose control of the vehicle and deviate from its intended trajectory.

Overall, the trajectory of a vehicle is influenced by several factors, and it is important for drivers to be aware of these factors and adjust their driving accordingly.

Drivers can maintain control of their vehicle and maintain the intended trajectory by driving at safe speeds, paying attention to the road and traffic conditions, maintaining their vehicle in good condition, and using defensive driving techniques to avoid accidents and collisions.

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