[Perencanaan Geometrik Jalan]: Alinyemen Horizontal

Summary

This video provides a comprehensive overview of horizontal road alignment design. It covers key topics such as the definition and components of horizontal alignment, centrifugal force, super-elevation, and transition curves. The script explains how these factors influence road design, with a focus on the forces acting on vehicles during turns, and how they are countered by friction, road geometry, and superelevation. The video also outlines different design methods and parameters, offering a clear understanding of road planning for safe and efficient travel.

Takeaways

• 😀 Horizontal alignment refers to the projection of the road axis on a horizontal plane and is known as the road trace or road alignment.
• 😀 The horizontal alignment consists of straight lines connected by curves, which can be circular arcs, transition curves, or a combination of both.
• 😀 Centrifugal force occurs when a vehicle moves along a curved path, pushing the vehicle outward and creating discomfort for the driver.
• 😀 The centrifugal force is counteracted by friction between the tires and road surface, and by the vehicle's weight due to the road's transverse slope (superelevation).
• 😀 The formula for centrifugal force depends on the vehicle's speed, vehicle weight, gravity, and curve radius.
• 😀 Key factors influencing centrifugal force include the radius of the curve (r), friction coefficient (f), and superelevation (e), all of which depend on the road design speed.
• 😀 Superelevation is the transverse slope provided on curves to counteract centrifugal force, and its value is typically between 8-10% depending on the road design and speed.
• 😀 The transition between straight sections and curved sections of roads involves transition curves to avoid sudden changes in direction, improving driving comfort.
• 😀 The length of a transition curve varies based on design standards (e.g., Binamarga or Asto), and it typically starts from a normal elevation and gradually reaches maximum superelevation before the curve.
• 😀 The design of horizontal curves must consider several factors: minimum radius, friction, superelevation, and curve degree. These elements are interconnected to ensure safe road conditions.
• 😀 Different types of horizontal curves exist, including full circles, spiral circles, and spiral-spiral curves, each with specific design criteria and applications in road planning.

Q & A

What is horizontal alignment in road planning?

Horizontal alignment is the projection of the road axis onto the horizontal plane. It includes straight lines connected by curves, which can be circular arcs or transition arcs.

What are the key elements of horizontal alignment?

The key elements of horizontal alignment include straight sections and curved sections. Curved sections are referred to as turns or curves in road design.

How does centrifugal force affect a vehicle on a curve?

Centrifugal force pushes a vehicle outward from its lane when it moves through a curve. This force can cause discomfort to the driver and might push the vehicle out of its lane if not properly balanced.

What factors balance the centrifugal force acting on a vehicle?

The factors that balance centrifugal force include friction between the vehicle's tires and the road surface, the weight of the vehicle, and the transverse slope (superelevation) of the road.

How is the minimum curve radius related to the planned vehicle speed?

The minimum curve radius is determined by the planned vehicle speed. For example, a speed of 100 km/h requires a minimum curve radius of 370 meters.

What is superelevation and why is it important in road design?

Superelevation is the transverse slope or banking of the road, designed to counteract centrifugal force on curves. It helps in preventing vehicles from skidding out of their lanes when navigating curves.

What factors influence the superelevation of a road?

The superelevation of a road is influenced by factors such as weather conditions, road surface conditions, and the topography of the area.

What is the relationship between the curve radius and the degree of curvature?

The curve radius and the degree of curvature are inversely related. A smaller radius results in a sharper curve and a higher degree of curvature, while a larger radius results in a gentler curve with a smaller degree of curvature.

How is friction between the vehicle's tires and the road surface related to centrifugal force?

Friction between the tires and the road surface helps counterbalance centrifugal force, preventing the vehicle from sliding out of the curve. The friction coefficient depends on factors like tire condition, road texture, speed, and weather.

What is a transition curve, and why is it important?

A transition curve is a gradual curve that connects a straight section of road to a circular curve. It is important for ensuring smooth transitions between different road shapes and preventing abrupt changes that could discomfort drivers.