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10 2. Project timelines were required to be within 23 years Truck-Related Bottleneck in Washington State--Washing- 3. Costs were required to be less than $15 million ton SR 167 in Federal Way in the Puget Sound region exhib- 4. Safety could not be decreased as a result of the project. ited a bottleneck caused by a steep grade that dramatically reduced truck speeds. A lane was added on the grade to Latham and Trombly (10) defined low-cost traffic engineer- accommodate slow-moving trucks. ing improvements to be "project(s) or strategy(ies) that Florida--An interchange with short weaving sections caused generally [require] an investment in the range of $10,000 to queuing on the ramp that often extended to the freeway $50,000." The authors also noted that "Low-cost traffic engi- mainline. The problem was addressed by adding a right-turn neering improvement techniques are typically spot applica- lane and a signalized right-turn lane. tions or are limited to shorter sections of roadway that do not Maryland's Quick Fix at Interstate 70/Interstate 695-- cover an entire length of an arterial corridor. Some of these Inadequate capacity of the I-70/I-695 interchange outside strategies include pavement markings, static and dynamic sign- of Baltimore, Maryland, resulted in traffic on the east- ing, roadway lighting, raised medians, curb cuts, roadway geo- bound approach from I-70 to I-695 backing up on to the metric changes, or lane controls. These strategies provide the mainline of I-70, restricting flow of through traffic. A guidance, warning, and control needed for drivers to ensure quick-fix solution was to widen the ramp up to the bridge. safe and informed operation through traffic bottlenecks or This provided adequate storage to relieve the backup onto congested areas." the mainline. Regardless of cost, three categories of improvements are identified in the literature: (i) physical, geometric, and engi- To reduce delays and improve highway access to a major neering improvements; (ii) operational and technology intermodal facility, Corwith Yard in Chicago, Illinois, the sig- improvements; and (iii) regulatory- or public policy-based nal system at the intersection was updated and synchronized improvements. The following sub-sections describe these three to allow trucks to make turns safely. These improvements categories and illustrate them with examples. eliminated the delays to trucks getting into the yard (13). 2.2.3 Examples of Physical 2.2.4 Low-Cost Operational/Technology Low-Cost Improvements Improvements Walters et al. (11) documented three case studies in Texas FHWA (14) suggests that improving the management and that are considered to be low-cost improvements. operations of transportation systems is a cost-effective way to influence the bottlenecks that affect freight. The following 1. Improvements to a section of an urban highway where 12 low-cost operational remedies have been identified (12): weaving and horizontal curve problems occur. To address the problem, an exit ramp was replaced with an entrance ramp to remove the weaving problem at a cost of $660,000. 1. Using a short section of the shoulder as an additional The improvement reduced the cost of delay on the ramp by travel lane $700,000 annually. 2. Re-striping the merge/diverge areas to better serve demand 2. Mobility constraint due to lane drop and weaving on a 3. Reducing lane widths to add a travel and/or auxiliary lane congested exit ramp. The low-cost improvement was to 4. Modifying weaving add an auxiliary lane so that the entrance/exit lane did not 5. Metering or closing entrance ramps end at the exit. This required a change in the designated 6. Speed harmonization (adjusted speed limits when use of an outside shoulder. The total cost was $150,000. congested) The benefits in delay mitigation were calculated to be 7. Zippering, self-metering that promotes fair and smooth $200,000 annually. merges 3. Addition of a lane to the inside shoulder in a highly con- 8. Improving traffic signal timing on arterials gested urban highway to add capacity. The cost of this addi- 9. Improving arterial corridors using access management tional lane was approximately $130,000, the majority of principles which was reported to be spent on re-striping the section 10. High Occupancy Vehicle (HOV) lanes of highway. The delay reduction benefits were calculated to 11. Providing traffic diverging information be $600,000 annually, and there was an additional safety 12. Implementing road pricing to bring supply and demand benefit found through a decrease in crashes at the location. into alignment. FHWA (12) also reported that similar low-cost improve- Ramp metering was ranked as the most utilized low-cost ments implemented elsewhere mitigated congestion. Examples operational improvement among transportation agencies. This include the following: is followed by auxiliary lanes and then HOV lanes. In general,