Trolley overheads are also susceptible to icing, especially when freezing temperatures hit a climate where moist ocean air is already present. The problem is usually detected before the start of service, so the first runs out of the yard are equipped with ice cutters on the carbons (the contacts at the end of the trolley poles). But the ice cutters can damage the overhead wires, so they must be used sparingly.
Considering the greenhouse impact of electric buses is a bit more complicated. Of course, the buses themselves don’t produce emissions, but one must consider how the electricity is produced. If the power comes from coal-fired plants or other sources regarded as dirty energy, then that has to be taken into account. TransLink’s trolley buses are run by hydroelectric power, which, all things considered, is regarded as relatively clean.
TransLink used a form of carbon offsets to purchase the new fleet of New Flyers. For the past few years, BC Hydro has offered Green Power Certificates (GPCs), which help pay the difference between the cost of conventional electricity production like hydroelectric dams and the cost of green production like windmills, waterfalls and biomass. In order for the Federation of Canadian Municipalities to guarantee a loan at below market interest to buy the buses, TransLink agreed to use the savings in interest payments to purchase GPCs. Thanks to a reduction in BC Hydro’s price for the GPCs and a volume-purchase discount to TransLink, the amount of green electricity produced with those GPCs more than offsets the amount of brown electricity consumed by the new trolleys.
As for urban rail, the SkyTrain and Canada Line systems are grade-separated — mostly elevated, with some underground sections. The obvious advantage to that is the ability to bypass traffic altogether, run at fairly high speeds (up to 50 miles per hour or 80 kilometers an hour) and operate in all weather. The construction costs are variable, but considerable: approximately US $120 million per mile elevated; an average of $200 million per mile for an underground system, and about $100 million per mile for the Evergreen Line, which will be largely at grade.
SkyTrain’s automated mini-metro technology was considered the best for the Vancouver area, expandable to carry up to at least 25,000 people per hour in each direction. Peak hour ridership now exceeds 10,000 passengers per hour (peak link, peak direction), equivalent to four full freeway lanes. Growth is effectively capacity-constrained until delivery of 34 additional cars in 2009, which will provide an additional 22 percent capacity. While fully segregated busways can move up to 15,000 people an hour, mixed traffic operation limits capacity. Vancouver’s three rapid bus lines have limited street priority, including curbside bus lanes, some signal priority and carry a maximum of 2,000 people per hour per direction.
One of the advantages to SkyTrain has been its driverless technology. Personnel are free to patrol the system, responding to situations like helping visitors understand the system, managing crowds during peak periods and even driving the trains when needed (SkyTrain attendants are certified motormen).
The trains are controlled from a central facility where operators monitor real-time computer displays, showing information on all of the trains in service. They are able to take control of trains at any time, while being aware of the locations of all the other trains on the system at once.
TransLink decided on light-rail transit for the Evergreen Line for a variety of reasons. While much of the urban growth mentioned earlier has been to the east and southeast of the city, the rate of growth of Greater Vancouver’s Northeast sector has surprised many people. The topography of the region, which is mountainous in some areas, does not allow for widening of roads. Neither, in fact, does public sentiment. Light rail offers high capacity, and since it travels at grade rather than above ground, it’s more compatible with community objectives.
For light-rail transit to operate effectively, it needs segregation from other traffic and traffic signal priority. The Evergreen Line’s per-mile cost is actually quite high, but it includes the cost of boring a 1 ½-mile (2 kilometer) tunnel in a location where the grade is too steep to negotiate at the surface.