A new approach for computing the uniform delay component based on incremental queue accumulation (IQA) has been presented in a companion paper to this one. The method is fully consistent with the intent of Webster's first delay term, and under the same assumptions as Webster's, produces identical results. The method provides added flexibility beyond what the purely analytical approach can handle, particularly in the complex cases of protected-permitted turns, two green times per cycle, and the effect of sneakers, among others. The companion paper provides analytical details of the methods, and numerical examples to illustrate its applications. This paper focuses on incorporating the effects of signal coordination (or lack thereof) on the uniform delay component in the context of the IQA approach. It is shown that the IQA method is fully capable of handling variable arrival rates in different parts of the cycle, and that under similar assumptions as the Highway Capacity Manual (HCM), would produce consistent results as well. An important finding in the course of this investigation was that the current progression adjustment factor in the HCM is based on the simplifying assumption that the uniform queue dissipates at the same point in the cycle, regardless of the level of coordination. Clearly this is an erroneous assumption that the IQA is now able to overcome. Taken together, the findings in this and the companion paper have outlined a rational, consistent and flexible uniform delay estimation procedure that is far superior to the current HCM approach. The approach has been endorsed by the Signalized Intersection Subcommittee (SigSub) of the TRB Highway Capacity Committee. The paper also details some of the considerations which will be needed in order to incorporate a lane-by-lane approach to signalized intersection capacity analysis. Such an approach has been proposed and endorsed by SigSub, and will require procedural changes which are best accomplished in parallel with the IQA changes.
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