Washington Avenue Extension (unsigned NY 910D) begins at an intersection with NY 155 (here county-maintained as CR 157) near the western Albany city line. The highway heads southeastward as a four-lane divided highway, paralleling the routing of nearby Interstate 90 (I-90) to New York State Thruway exit 24. This portion of Washington Avenue Extension is flanked on both sides by named Frontage Roads, both of which begin at NY 155. The northern road ends prior to Rapp Road while the southern road ends just short of Crossgates Mall.