Rail clip prisms glowing at dusk

GEO's AMTS is monitoring Caltrain track during adjacent construction. The dots of light are prisms installed on the track.

Installing rail clip prisms

Rail clip prisms are installed in pairs at 15-foot intervals along the track. This photo shows only the inside prisms.

Road prisms at crossing

Pairs of road prisms at the road crossing. Monitoring prism pairs provides measurements of track geometry, which should remain stable during the construction.