With the recent increase in the number of bicycles on our nations' highways and streets, there has been a corresponding increase in the number of bicycle accidents. Some of these accidents are related to highway grate inlets. The purpose of the comprehensive study summarized in this paper was to identify develop, and analyze selected grate inlets that maximize hydraulic efficiency and bicycle safety. Fifteen grate inlet designs were initially selected for consideration. They included seven steel-fabricated grates and eight cast grates. The test program was conducted using two test facilities. The bicycle safety tests were conducted on an outdoor test site consisting of a 6.7-m (22-ft wide, 152-m (500-ft) long abandoned roadway. A 2.44-m (8-ft) wide, 18.3-m (60-ft) long hydraulic test flume was constructed in the US Bureau of Reclamation, Hydraulic Research Laboratory, and used as a test facility for the hydraulic efficiency tests. The tests showed that, above certain longitudinal slopes, hydraulic efficiency was adversely affected. Also, debris-handling ability improved as the longitudinal bar spacing widened; while deterioration in bicycle safety performance began as transverse bar spacing increased above 102 mm (4 in.).