Yes, you can usually ship boxes or personal items in your car when it's being transported, but there are a few important considerations:

1. Carrier Policies: Byroad Logistics allow you to ship personal belongings inside the vehicle, but they may have weight limits (usually around 100-150 pounds) and restrictions on what can be placed in the car. 
2. Insurance Coverage: Items inside the car are often not covered by the car shipping company’s insurance, so if you decide to ship boxes, they may be at your own risk. You may need to look into additional insurance options.
3. Access and Inspection: The driver or shipping company may need to inspect the vehicle and its contents before shipping. Additionally, the boxes should be secured and placed in a way that doesn't obstruct the driver's view or access to the vehicle.
4. Security Risks: Shipping valuable or fragile items inside your car is generally not recommended due to the risk of theft or damage during transport.
5. Weight Considerations: The additional weight from the boxes could affect the cost of shipping, as some companies may charge extra if the car exceeds a certain weight limit.