Many urban streets in Taiwan were designed as viaducts to minimize conflicting traffic movements. The off-ramps of these viaducts or bridges usually ended at or near their immediately downstream signalized intersection. The queue discharge characteristics and the resulting lane capacities at such intersections may be affected by the adjacent off-ramp grades. To take the impact of grade into consideration, Taiwan Highway Capacity Manual (THCM) applies grade adjustment factors to estimate queue discharge rates justifying the upstream grades on the intersection approach lanes. The grade adjustment factors used in THCM, however, have not been validated using local traffic data. Therefore, this study analyzed the queue discharge characteristics on downgrade straight-though lanes using data collected at eight sites in Taipei area. It was found that downgrade significantly increases queue discharge ability, and the parameter of discharged passenger-cars per signal cycle, Ngyi, could be reasonably estimated by green interval, g, in the signal cycle using the analyzed regression equations. Furthermore, various roadway geometric effects on queue discharging were also discussed. The findings of this study could provide better insight into the effects of grade on queue discharging in Taiwan.