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53 Problem Likely Cause Solution Strategies Improvement Alternatives Excessive Variability in Demand exceeds capacity, Reduce probability of Bring road design up to agency standards Peak Travel Times and incidents are too incidents. Accident history investigation frequent and too damaging Vehicle regulations Reduce roadside distractions Reduce in-vehicle distractions Reduce incident detection Real-Time Monitoring of traffic flow times. Improve emergency Establish roving response teams response times. Service patrols Reduce incident clearance Integrate 911 emergency responders and times. maintenance operations Contract towing services dedicated to road sections Off-road pullouts for exchanging accident info Reduce impacts of incidents Wider shoulders on capacity. Off-road pullouts for exchanging accident info Gawker Screens Traveler information systems to help people avoid incident locations. Exhibit 7.2. Alternative improvements to solve reliability problems. 3. TCRP Report 95: Traveler Response to Transportation Sys- 7.5 Evaluation of Alternatives tem Changes. Includes discussion of transit scheduling and frequency, Once the problem to be solved has been defined, the and other operational actions that impact ridership. performance measures selected, and the alternatives to be eval- 4. TCRP Report 100: Transit Capacity and Quality of Service uated have been identified, then the evaluation of the effec- Manual, Second Edition, TRB, Washington, D.C., 2003. tiveness of each alternative is generally quite straight forward. This comprehensive manual includes information on The analyst uses the methods described in Chapters 2 and capital and operating strategies for bus, rail, and water 3 to estimate the travel-time, delay, and reliability measures transit, covering vehicles, routes/alignments, and stations. that will be used to compare the performance of each im- provement alternative. For example, if analysts were to define their problem as ex- 7.4 Selection of Performance cessive delay and excessive unpredictability in the delay, then Measures they might select the mean person-hours of delay and the Performance measures (also called measures of effective- variance in the person-hours of delay as their performance ness, or M.O.E.) are the system performance statistics that best measures. The analyst might then develop four alternative im- characterize the degree to which a particular alternative meets provement strategies for addressing the problem. They might the agency's objectives. Chapter 2 describes the selection of be: do nothing, add capacity (Alt. A), manage demand appropriate measures of effectiveness for evaluating current (Alt. B), and improve incident response (Alt. C). Computa- operations, future operations, and alternatives for reducing tion of the person-hours of delay and their variance might travel time, delay, and variability. present results like those shown in Exhibit 7.3. (Person-hours The selected set of performance measures should be as traveled are shown as well as delay, because the total person- sparse as possible, consistent with the defined problem. A hours traveled is needed to obtain delay.). large set of measures strains the analyst's resources and The question then becomes, "Which alternative is best?" increases the probability of conflicting results, clouding the If simply looking at the mean person-hours traveled, then selection and prioritization process. you would select Alternative A as the best, since it provides