The terms 'unreliability' and 'congestion' are often used synonymously. However, a congested network is not necessarily unreliable. It is recognized, however, that control actions that reduce congestion can improve reliability. Similarly, any control actions that improve reliability can reduce congestion. In this paper, the reliability criteria is applied for the field assessments of several ramp metering strategies implemented on the A6W motorway in Paris, and the travel time reliability is improved using the ramp metering techniques.