Introduction:
When deciding which road is easier to ride a bicycle on, we need to consider factors such as surface condition, traction, and comfort. In this scenario, we have three different roads to choose from: a gravel road, a road with oil spills, and a smooth concrete road. Let's analyze each road and determine which one is the easiest to ride a bicycle on.

Gravel Road:
Riding a bicycle on a gravel road can be challenging due to several reasons:
1. Surface Condition: Gravel roads are characterized by loose stones, making it difficult for the bicycle tires to maintain traction. This can lead to skidding, especially while cornering or braking.
2. Traction: The loose gravel surface reduces the grip between the bicycle tires and the road, making it harder to pedal and maintain stability. This can result in a higher risk of accidents.
3. Comfort: Riding on a gravel road can be uncomfortable due to the constant vibrations caused by the uneven surface. This can lead to fatigue and discomfort, making the journey more challenging.

Road with Oil Spills:
Riding a bicycle on a road with oil spills can also pose difficulties:
1. Surface Condition: Oil spills create a slippery surface, reducing the grip between the bicycle tires and the road. This lack of traction can make it challenging to maintain balance, especially when turning or braking.
2. Traction: The presence of oil spills decreases the friction between the tires and the road, making it harder to pedal and control the bicycle. This can lead to skidding and loss of control, increasing the risk of accidents.
3. Comfort: The slippery surface of an oil spill road can cause vibrations and jolts, leading to discomfort and fatigue. This can make the journey more physically demanding and less enjoyable.

Smooth Concrete Road:
Out of the three options, a smooth concrete road is the easiest to ride a bicycle on due to the following reasons:
1. Surface Condition: The smooth concrete surface provides better traction and grip, allowing the bicycle tires to maintain stability. This reduces the risk of skidding and provides a more predictable riding experience.
2. Traction: The higher friction between the tires and the smooth concrete road allows for easier pedaling and efficient transfer of power. This makes it easier to maintain a steady pace and control the bicycle.
3. Comfort: The smooth surface of a concrete road minimizes vibrations and jolts, providing a more comfortable riding experience. This reduces fatigue and allows the rider to enjoy the journey.

Conclusion:
In conclusion, when considering the ease of riding a bicycle, a smooth concrete road is the most preferable option out of the three roads mentioned. Its better surface condition, increased traction, and enhanced comfort make it the ideal choice for a smooth and enjoyable ride. However, it is important to always prioritize safety and follow traffic rules regardless of the road surface.