The dowel is used in rigid pavements for transferring load from one portion to another. In this context, the term "dowel" refers to a short cylindrical rod or pin that is typically made of steel and is placed across joints in concrete pavements. These dowels play a crucial role in ensuring the overall performance and longevity of the pavement structure.

1. Purpose of Dowels in Rigid Pavements:
- Transferring Load: One of the main functions of dowels is to transfer load from one section of the pavement to another. This is particularly important at transverse joints, where two adjacent concrete slabs meet. The dowels allow for the movement of the slabs due to temperature changes, traffic loads, and shrinkage, while ensuring that the load is evenly distributed across the joint.

2. Load Transfer Mechanism:
- Axial Load Transfer: Dowels are designed to transfer axial loads, which are the vertical loads applied on the pavement surface by vehicles. By providing a continuous load transfer mechanism, dowels help prevent differential vertical movement between adjacent slabs and minimize the development of cracks and faults in the pavement.

3. Types of Dowels:
- Round Dowels: Round dowels are commonly used in rigid pavements and are typically placed at regular intervals along the transverse joints. They are usually made of steel and have a smooth surface to facilitate movement and load transfer.
- Plate Dowels: Plate dowels are another type of load transfer device used in rigid pavements. They consist of rectangular or square steel plates that are inserted into the concrete slabs at the joints. Plate dowels offer increased load transfer capacity and better control of joint movements compared to round dowels.

4. Advantages of Dowels in Rigid Pavements:
- Prevents Cracking: By effectively transferring loads, dowels help prevent the formation of cracks and faults at the joints. This ensures the structural integrity of the pavement and reduces the maintenance requirements.
- Improves Performance: Proper load transfer through dowels improves the overall performance of the pavement by reducing the stresses on the concrete slabs and enhancing their durability.
- Enhances Ride Quality: By minimizing differential vertical movement between adjacent slabs, dowels contribute to a smoother and more comfortable ride for vehicles.

In conclusion, dowels are essential components in rigid pavements as they play a vital role in transferring load from one portion of the pavement to another. They help maintain the integrity of the pavement structure, prevent cracking, and improve the overall performance and longevity of the pavement.