Reliability — When this ride is open and running, how often does it break down? A ride with 98% reliability almost never breaks down during its operating hours. The grade is based on this metric.

Availability — What percentage of total park hours is this ride actually open and running? Some rides have restricted hours (outdoor coasters close for weather, some rides don't operate all day). A ride can have high reliability but lower availability if it simply isn't scheduled to run all day.