Operation of Traffic Signal Systems in Oversaturated Conditions, Volume 2 – Final Report (2014) / Chapter Skim
Currently Skimming:
Pages 279-293
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 279... ...
Chapter 4: Conclusions and Future Directions In this project, Dr. Douglas Gettman at Kimley-Horn and Associates (KHA)
|
From page 280... ...
dissipating overflow queuing from the previous cycle. Oversaturated routes, arterials, intersections, networks, and so on are then defined as having TOSI and/or SOSI > 0 on the constituent approaches and movements at the same time.
|
From page 281... ...
both. At some point, however, no further revision to the signal timing will increase maximum throughput and queues will continue to grow until demand diminishes.
|
From page 282... ...
During the recovery regime, traffic volumes and/or route proportions and/or restrictive downstream capacity (e.g. clearance of crash, removal of construction cones, reduction in traffic flow, etc.)
|
From page 283... ...
In addition to this structured and mathematically-based development methodology, we tested a variety of potential mitigations including phase reservice, negative offsets, cycle time adjustment, left-turn treatment, phase sequence, dynamic lane allocation, and phase truncation using engineering judgment. After identifying the critical routes for a specific scenario, combinations of mitigations were tested on four different simulation test cases.
|
From page 284... ...
identify appropriate actions. The guide concludes by specifying a generic systems-engineering-based process for deploying methodologies and evaluating their relative effectiveness.
|
From page 285... ...
From the identification of these critical routes and the approximation of the arrival demands on the routes, an optimization problem is solved to obtain a range of feasible cycle, split, offset values that meet an operational objective (minimize delay, maximize throughput, or manage queues)
|
From page 286... ...
critical movements and considered a sequence of timing plan changes at the beginning of the processing regime and then at the beginning of the recovery regime. The timing plan strategies considered green flaring, phase reservice, negative and simultaneous offsets, and harmonic (2:1 and 3:1)
|
From page 287... ...
Test Cases for Direct Application of TOSI and SOSI to Re-allocate Green-Time In the test applications for direct application of the TOSI and SOSI measures, we found significant improvements were possible. In the TH55 in Minneapolis, MN application, the TOSI and SOSI values were used to identify offset and green-time re-allocation recommendations to improve the throughput performance.
|
From page 288... ...
explore improvement of performance to non-critical routes that were previously blocked by vehicles on the critical routes using the standard operations. This test case also demonstrated how the on-line calculation of TOSI and SOSI measures with if…then logic could be used to select appropriate mitigation strategies in a closed-loop manner.
|
From page 289... ...
Project Summary and Directions for Further Research This goal of this project was to conduct research and develop guidance for practitioners in the application of mitigation strategies for oversaturated conditions. The body of knowledge in this area was quite limited when the project began.
|
From page 290... ...
measurements. This process was developed and tested in an off-line manner in this project and shown to make improvements to an oversaturated scenario.
|
From page 291... ...
Figure 179. Comparison of output processing rates during recovery period It is quite clear that the mitigation strategy begins processing more of the overflow queues much more efficiently after the peak period input flows subside.
|
From page 292... ...
every type of treatment. While the real-world cases that were tested in this project are instructive, for the most part it is difficult to extrapolate specific results from a particular test to other scenarios.
|
From page 293... ...
oversaturated conditions in actuated-coordinated systems would be of benefit to the industry. The FBP could be extended to a rolling-horizon formulation to take another step in that direction.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.