transportation
Transportation plays an essential role in the way societies function with significant impacts to the economic, social, political, and envi- ronmental sectors. It is undeniable that the need for robust, efficient, and sustainable transportation infrastructure remains a critical goal to support national and global advancements and is even more paramount with increasing population. Cities and economies must develop and evolve in innovative ways to meet the constraints of such opportunities and growth. For developing countries to advance their transportation systems, they can look to adopt emerging global innovations and technologies. My engineering education and career began in Ghana, a developing country located in West Africa. Ghana has one of the fastest growing economies on the continent, and similar to other countries, has multiple opportunities for transportation infrastructure development. Having now lived in the United Kingdom and United States, I have gained more insight into how efficient transportation systems directly impact a nation’s development. In a recent case study, we explored traffic-signal based strategies and innovative intersection designs for operational performance improve- ment. The case study focused on an existing intersection in Kumasi, the second largest metropolis in the country, and utilized capacity analysis, simulation, and modeling expertise for analyses. This case study was presented at the first Ghana Infrastructure Conference organized in Au- gust 2018 (GIC-2018) by the Ghana Transportation Professionals Fo- rum of North America (GTPF) and its local engineering and academic partners. The goal of the conference was to explore best practices in infrastructure development as well as to engage leaders and key stake- holders in Ghana and to set forth a collaborative process to facilitate and effect change. Study Location & Description The case study focused on the Anloga intersection along the main divided arterial entering Kumasi from the capital city of Accra. It is a major signalized four-leg at-grade intersection of the Accra-Kumasi Road (East-West approach) and the Eastern Bypass (North-South ap- proach). The existing intersection is characterized by recurring conges- tion, significant pedestrian volumes, long queues, low saturation rates, high side friction, and high left turn volumes predominantly during the morning and afternoon peak periods. The main east-west arterial has left turn lanes with protected left turn movements while the north- south Eastern bypass has left turn lanes and operates on a split phase. It operates on a fixed signal timing plan. Prior studies and plans have Towards Transportation Infrastructure Advancement in a Developing Country
Figure 1: Existing Anloga Intersection
identified the location for a potential design modification to an inter- change design. Various existing land use types and features as well as right-of-way costs could make an interchange a high cost alternative. Analysis Methodology The study methodology included a four-step process comprising data collection, planning level analysis, preliminary operational analysis, and microsimulation operational analysis. Data Collection Geometric data for the site was collected via aerial images, site obser- vations, and photos. Traffic data collected included volumes with clas- sification, queues, travel times and speeds, and signal timings during the morning and afternoon peak periods. Planning Level Analysis The Planning Level Analysis involved the use of the Federal Highway Administration (FHWA) Capacity Analysis for Planning of Junc- tions (CAP-X) spreadsheet tool. The tool utilizes critical lane volume analysis to examine the suitability of various configurations based on existing traffic volumes. For the purposes of this case study, only the more congested morning peak period was analyzed. The results showed that the existing conventional at-grade intersection design was the lowest ranked option out of the 15 intersection types tested. The top five design options all had volume to capacity (v/c) ratios less than 0.7 and included three and two variants of the Displaced Left Turn (DLT) / Continuous Flow Intersection (CFI) and Quadrant Roadway Intersection designs, respectively. Continuous flow intersections (CFI) also called Displaced Left Turns (DLT) function primarily through the relocation of the left-turn movements on an approach to the opposing roadway at crossovers upstream of the main signalized intersection thereby eliminating the left-turn phase for the approach at the main intersection and subsequently providing more green time for the con- secutive movement of left and through vehicles. A Quadrant Roadway Intersection (QRI) is typically a feasible option for the intersection of two busy suburban or urban roadways and works by adding two three- way intersections to the existing four-way intersection by rerouting turning movements from the main intersection onto a new roadway that connects the two intersecting roads.
17
may 2020
csengineermag.com
Made with FlippingBook Annual report