After 18 months of work, the entire original side-worn shelf on the Green Line was eliminated (see Figure 4) at a total cost of $1.2 million. While an expensive proposition, it saved the MBTA $13 million over the rail replacement/full-depth track reconstruction scenario. In addition to that, the low-floor car operation was able to resume at least a year earlier than it would have been without grinding.

The problem, however, was not immediately solved. The rail shelf began to redevelop almost immediately. This was caused by the mixed population of 63-degree and 75-degree wheel profiles that operated on the Green Line during the fleet-wide transition to the IWP. It was also due to the extremely flat running surface of the rail on the Green Line, which encouraged contact by the wheel flanges to the gauge side of the rail (see Figure 5). ARM and the MBTA determined that the only way to prevent redevelopment of the rail shelf would be to convert the entire Green Line fleet to the IWP and initiate rail profile grinding to minimize wheel flange contact with the rail. ARM and its consultant RESCO Engineering designed rail profiles to match the IWP and accommodate the handling characteristics of the low-floor vehicles.