Replace all remaining light bulbs in the metro system with LEDs (there are still significant non-LED lights around the system, including in the Bethesda metro stop). This will likely pay back within a year or 2 by energy savings alone and could generate significant savings to put to other meaningful initiatives.
Incandescent lights use significant amounts of energy, generate tons of waste heat, require enormous amounts of man hours to replace, contribute to air pollution and climate change, and waste much of WMATA's budget. The metro system has already seen significant LED retrofits, but progress is slow. The "cost of waiting" is high - especially since the price of LEDs has declined so much that these projects likely pay back from energy savings alone within a year. Now is the time to complete the job and generate savings for WMATA to put to better use.