Longish answer (mostly cribbed from Wikipedia)
Railroad electrification in the United States began at the turn of the 20th century and comprised many different systems in many different geographical areas, few of which were connected. Despite this situation, these systems shared a small number of common reasons for electrification.
Impetus for electrification
The common reasons for electrification in the United States include:
Laws banning steam locomotives (smoke abatement)
A number of municipalities passed laws in the early part of the 20th century forbidding steam locomotives from operating within city limits, after some bad accidents caused by the awful conditions of visibility in smoke and steam-filled tunnels and cuttings. The most prominent of these laws was for New York City in 1903 (effective 1908).
An extensive study was also undertaken in Chicago of the problems of smoke and the feasibility of electrification as a solution.
Long tunnels
Long, deep tunnels provide poor ventilation for steam locomotives, to the point where crews had to wear oxygen masks to avoid asphyxiation. The ventilation problem also limited the frequency of trains through these tunnels. The Cascade Tunnel is a good example. Also see the proposed North–South Rail Link.
Mountains
The electric locomotive has many advantages in mountainous terrain, including better adhesion, greater power at low speeds, no requirements for fueling or watering, and regenerative braking. The planned California High-Speed Rail system, for example requires electrification to achieve acceptable speeds through the Tehachapi Mountains.
Traffic density
Extremely high-traffic lines can readily recoup the high capital investment of electrification by the savings accrued during operation. The savings typically result from improved utilization of trains, and lower maintenance costs.
Short-distance commuter operations
Suburban commuter trains are an ideal subject for electrification since electric multiple units possess rapid acceleration, fast braking (sometimes regenerative braking) and the ability to change direction without running a locomotive around. It also reduces diesel locomotive emissions in relatively high-density areas.
Freight operations
Heavy freight trains are ideally suited to electric traction due to the greater pulling power of an electric locomotive.
Overview of electrification in the U.S.
Electrification in the US reached its maximum of 3,100 miles (5,000 km) in the late 1930s.
By 1973 it was down to 1,778 route miles (2,861 km) (Class I railroads) with the top 3 being: Penn Central 829 miles (1,334 km), Milwaukee Road 658 miles (1,059 km), Long Island Rail Road 121 miles (195 km).
In 2013 the only electrified lines hauling freight by electricity were three short line coal haulers (mine to power plant) and one switching railroad in Iowa.[9] The total electrified route length of these four railroads is 122 miles (196 km). While some freight trains run on parts of the electrified Northeast Corridor and on part of the adjacent Keystone Corridor, these freight trains use diesel locomotives for traction. The total electrified route length of these two corridors is 559 miles (900 km).
Advantages
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No exposure to passengers to exhaust from the locomotive
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Lower cost of building, running and maintaining locomotives and multiple units
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Higher power-to-weight ratio (no onboard fuel tanks), resulting in
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Fewer locomotives
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Faster acceleration
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Higher practical limit of power
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Higher limit of speed
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Less noise pollution (quieter operation)
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Faster acceleration clears lines more quickly to run more trains on the track in urban rail uses
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Reduced power loss at higher altitudes (for power loss see Diesel engine)
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Independence of running costs from fluctuating fuel prices
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Service to underground stations where diesel trains cannot operate for safety reasons
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Reduced environmental pollution, especially in highly populated urban areas, even if electricity is produced by fossil fuels
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Easily accommodates kinetic energy brake reclaim using supercapacitors
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More comfortable ride on multiple units as trains have no underfloor diesel engines
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Somewhat higher energy efficiency in part due to regenerative braking and less power lost when “idling”
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More flexible primary energy source: can use coal, nuclear, hydro or wind as the primary energy source instead of oil
Disadvantages
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Adding electric catenary to older structures may be an expensive cost of electrification projects
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Most overhead electrifications do not allow sufficient clearance for a double-stack car. Each container may be 9 ft 6 in (2,896 mm) tall and the bottom of the well is 1 ft 2 in (356 mm) above rail, making the overall height 20 ft 2 in (6,147 mm) including the well car.
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Electrification cost: electrification requires an entire new infrastructure to be built around the existing tracks at a significant cost. Costs are especially high when tunnels, bridges and other obstructions have to be altered for clearance. Another aspect that can raise the cost of electrification are the alterations or upgrades to railway signaling needed for new traffic characteristics, and to protect signaling circuitry and track circuits from interference by traction current. Electrification may require line closures while the new equipment is being installed.
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Appearance: the overhead line structures and cabling can have a significant landscape impact compared with a non-electrified or third rail electrified line that has only occasional signaling equipment above ground level.
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Fragility and vulnerability: overhead electrification systems can suffer severe disruption due to minor mechanical faults or the effects of high winds causing the pantograph of a moving train to become entangled with the catenary, ripping the wires from their supports. The damage is often not limited to the supply to one track, but extends to those for adjacent tracks as well, causing the entire route to be blocked for a considerable time. Third-rail systems can suffer disruption in cold weather due to ice forming on the conductor rail.
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Theft: the high scrap value of copper and the unguarded, remote installations make overhead cables an attractive target for scrap metal thieves. Attempts at theft of live 25 kV cables may end in the thief’s death from electrocution. In the UK, cable theft is claimed to be one of the biggest sources of delay and disruption to train services — though this normally relates to signaling cable, which is equally problematic for diesel lines.
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Birds may perch on parts with different charges, and animals may also touch the electrification system. Animals fallen to the ground are fetched by foxes or other predators [27], bringing risk of collision with trains.
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In most of the world’s railway networks, the height clearance of overhead electrical lines is not sufficient for a double-stack container car or other unusually tall loads. It is extremely costly to upgrade electrified lines to the correct clearances (21ft 8 in or 6,630mm) to take double stacked container trains.
World electrification
In 2006, 240,000 km (150,000 mi) (25% by length) of the world rail network was electrified and 50% of all rail transport was carried by electric traction.
In 2012 for electrified kilometers, China surpassed Russia making it first place in the world with over 48,000 km (30,000 mi) electrified.[28] Trailing behind China were Russia 43,300 km (26,900 mi), India 35,488 km (22,051 mi), Germany 21,000 km (13,000 mi), Japan 17,000 km (11,000 mi), and France 15,200 km (9,400 mi).
Summary
Why won’t GoTriangle electrify despite overwhelming environmental evidence of its benefit?
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Unlike Denver, there is no political will to make it happen.
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There is a traditional stakeholder – namely the North Carolina Rail Road and its tenant, Norfolk Southern, who see no benefit in electrification.
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Semi-frequent hurricanes and ice storms might prove to be an environmental hindrance to stringing up overhead catenary lines which would be prone to damage.
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And, GoTriangle is going to take the most cautious approach this time around to try and get things right. They’ve been burned twice before, and have taken a very public drubbing for their prior failures. If their efforts fail, then it will be another generation before this question comes up again.
