From the USPS Office of the Inspector General:
The number of city carriers returning after 5 p.m. is a growing problem in the Capital District, increasing by 14 percent from FY 2011, Quarter 1 to FY 2013, Quarter 4. City carriers returned after 5 p.m. because mail coming from processing facilities did not always meet times established in the integrated operating plan and management did not always properly supervise city delivery operations. Adhering to integrated operating plans will improve mail arrival time at delivery units. Further, better supervision of city letter carriers will reduce the number of carriers returning after 5 p.m., increase carrier safety, and reduce late mail delivery.
In other matters, external stakeholders suggested the Postal Service take additional safety measures such as providing brightly colored, reflective clothing to make city carriers more visible and identifiable in the dark. Other suggestions included providing additional safety training and realigning delivery routes so carriers can deliver mail earlier in the day in dangerous areas.
Full report (.pdf format)