Bird's-foot Trefoil or Birdfoot deer vetch:
Lotus corniculatus L.
Driving home from Indiana University of Pennsylvania provided a new highway flower for my repertoire. This pretty yellow flower is prevalent alongside the PA turnpike... its called birds-foot trefoil. Planted by the Turnpike administration to prevent erosion, it is a member of the legume family and is very hardy. It grows in poor soil (sandy or clay), populates in many ways, long tap root, and tolerates salt. Pretty. A weed to many but a pretty splash of color along the road. The last picture is courtesy of the USDA website.