Numerous studies on Honolulu’s rail project have all reached the same conclusion: at-grade light rail cannot deliver fast, frequent, safe and reliable transit service for Oahu. This is why the Honolulu City Council, after carefully considering all options, chose a grade-separated system. The Federal Transit Administration reviewed the city’s research and independently validated the conclusion.

In contrast, the recent Honolulu Transit Task Force (HTTF) paper advocating for an at-grade rail system (“Taking it to the streets,” Star-Advertiser, Feb. 5) does not take into account the numerous engineering studies, technical reports and reviews that support Honolulu’s grade-separated project.

Building an at-grade rail system would not be as inexpensive as the HTTF report touts. Based on an assessment of construction costs of new at-grade systems like Phoenix, the true building cost of HTTF’s proposal is hundreds of millions of dollars more than indicated in its paper.

A major flaw in HTTF’s report is using 2008 mainland construction costs as the basis of its cost projections, instead of current Hawaii costs. Remember that 2008 was the start of the recession when construction costs were nearing their lowest levels within a typical construction cycle. Hawaii today is near the top of the current cycle, where costs are typically at their highest.

The HTTF report also got it wrong on long-term operating costs. An at-grade light rail system is more expensive to operate and maintain than an elevated system. It is slower, needs more trains to match capacity, and has additional costs for its drivers and operators, which are largely absent in Honolulu’s automated system.

An at-grade rail system would likely have significant cultural impacts. Building an at-grade route would require digging a road trench approximately 30-feet wide and anywhere from 2- to 7-feet deep on Dillingham Boulevard, through downtown and in Kakaako. Potential human burial sites and cultural artifacts are most often found at depths of 5 feet or less. This means more archaeological resources along the route would likely be impacted by an at-grade rail system than one that is elevated, where excavation is limited to 8-foot diameter columns every 100 feet or more along the route.

Safety is another concern. Phoenix’s Valley Metro ground-level rail system had more than 20 vehicle-train collisions in its first six months. Seattle’s at-grade systems in Sodo and Rainier Valley, which began service in 2009, have had 51 Link-involved crashes, including eight fatalities.

The most serious impact is that at-grade trains would be as slow as the surrounding traffic. Trains would be stuck in the same congestion, would be stopped at the same red lights, and have to wait for the same pedestrians to cross the street.

The reality is that the Honolulu City Council, based on accurate and detailed information, chose the best technology for Honolulu’s rail system. Rehashing old arguments won’t get us any closer to an operating rail transit system for Hawaii, and it will most certainly delay the project, increasing costs and frustrations. A sound decision has been made. It is easy to be the Monday morning quarterback. But at this point, we are beyond that.

Krishniah Murthy is interim executive director/chief executive officer of the Honolulu Authority for Rapid Transportation.