WHY CURVED ROADS ARE BANKED

If you’ve ever been on a winding road, you may have noticed that the road is often banked, or tilted towards the outside of the curve. This is done for a reason: to help keep vehicles from skidding off the road.

1. What is Banking?

Banking is the practice of inclining the surface of a road or race track towards the outside of a curve. The angle of the bank is typically between 2 and 5 degrees, but can be as steep as 15 degrees on some racetracks.

2. Why Bank Roads?

There are two main reasons why roads are banked. First, banking helps to keep vehicles from skidding off the road. When a vehicle rounds a curve, the centrifugal force acting on it pushes it towards the outside of the curve. If the road is not banked, the vehicle will have to rely on its tires to keep it from skidding. However, if the road is banked, the force of gravity helps to keep the vehicle in its lane, reducing the likelihood of a skid.

Second, banking helps to reduce the rollover risk. When a vehicle is rounding a curve, its outside wheels are traveling a greater distance than its inside wheels. This can cause the vehicle to lean towards the outside of the curve, which can lead to a rollover. However, if the road is banked, the angle of the bank helps to keep the vehicle's weight distributed evenly, reducing the risk of a rollover.

3. How Much Banking is Needed?

The amount of banking needed depends on a number of factors, including the speed limit, the radius of the curve, and the coefficient of friction between the tires and the road surface. In general, the higher the speed limit, the sharper the curve, and the lower the coefficient of friction, the greater the amount of banking that is needed.

4. Special Considerations for Steep Banking:

• Sightlines: Steep banking can make it difficult for drivers to see oncoming traffic, especially at night. To address this issue, engineers often use longer sightlines on banked roads, allowing drivers to see further down the road.
• Drainage: Steep banking can also make it difficult for water to drain off the road surface, which can lead to hydroplaning. To prevent this, engineers often use special drainage systems on banked roads.
• Vehicle Stability: Steep banking can also affect the stability of vehicles, especially motorcycles and bicycles. To ensure that vehicles remain stable on banked roads, engineers often use special signs and pavement markings to alert drivers to the presence of the bank.

5. Banking on Race Tracks

Banking is also used on race tracks to help drivers maintain higher speeds through corners. The steeper the banking, the faster drivers can go without losing control of their vehicles. Some race tracks, such as the Indianapolis Motor Speedway, have banks that are as steep as 15 degrees.

Conclusion

Banking is an important safety feature on curved roads. It helps to keep vehicles from skidding off the road and reduces the risk of rollovers. The amount of banking needed depends on a number of factors, including the speed limit, the radius of the curve, and the coefficient of friction between the tires and the road surface.

Frequently Asked Questions

1. Why are some curved roads banked while others are not?
2. What is the purpose of banking a road?
3. How much banking is needed on a curved road?
4. What are some of the challenges associated with banking roads?
5. How does banking affect the stability of vehicles?