SCCA® Solo® has many categories divided into classes for vehicles. Those categories include:
- Street – This category provides the lowest barrier of entry and appeal to the largest segment of potential and existing members. Preparation allowances are limited to those with a minimal impact on daily public highway use of the vehicle.
- Street Touring – Competitors in this category are looking to add performance through bolt-on components compatible with public highway use. This category incorporates popular enthusiast modifications for public highway and autocross use.
- Street Prepared – Street Prepared builds on the Street allowances to provide opportunities for vehicles with more extensive modifications that may not be suitable for public highway use. This category includes the lower-prep category allowances plus a moderate level of fabrication and a greater range of bolt-on alternatives.
- Street Modified – Street modified allows competitors to modify vehicles using advanced fabrication and tuning with specific limitations. Street Modified provides the allowances of the lower-prep categories with the addition of major modifications to the drivetrain, suspension, and body as well as sophisticated aerodynamic components.
- Prepared – Competitors in this category are permitted broad modifications and fabrications opportunities in suspension, drivetrain, and engine with no expectation of public highway use. This category allows for the development of purpose-built competition vehicles based on production cars, including true racing slicks, weight reduction, and extensive modifications to chassis and powertrain.
- Modified – The Modified category provides a competitive outlet for the highest level of allowed modifications. This allows for purpose built competition vehicles, with allowances for a wide variety of designs and origins.
- Kart Modified – This category is an outlet for members interested in running karts at Autocross events. Preparation allowances are in line with national karting organizations to allow for easy migration between Solo and other karting events.