In a period of reduced funding for roadway construction projects, the cost effectiveness of many design elements should be reviewed as engineering consultants strive to assure operational integrity and safety of the roadway. One of these elements is emergency power backup for tolling sites, including open road tolling (ORT), managed/express lanes, and traditional tolling facilities. A cost-benefit analysis must be performed to determine if the installation of power backup resources for tolling components is a financially viable solution. If it does not make financial sense, then it should be eliminated from the design.
Low-cost Uninterruptible Power Supplies (UPS) systems typically provide short-term (up to one hour) of conditioned emergency power when the input power source fails. Some UPS systems only supply several minutes of power while emergency generators or other standby power sources begin operation to support full power. These generators can deliver power for several days, if not weeks, but are costly to purchase, install, and maintain. For some tolling sites, the installation of a generator and associated fuel source is not cost-effective, because the expense far exceeds the potential revenue lost during an outage. These costs include civil/electrical design and installation, routine maintenance, and procurement in addition to the safety measures for securing the fuel source. However, for mainline plazas at high volume and revenue locations, emergency power may be a good option.
When conducting the cost-benefit analysis, engineers should consider the financial impact from short-term power outages and catastrophic regional failure supplemented with risk analysis. One such catastrophic failure was the Northeast US power outage in August 2003. This was a widespread power outage that occurred throughout parts of the Northeastern and Midwestern US and the Canadian province of Ontario, fortunately, the power of many toll agencies was not greatly affected due to the large-scale emergency power sources, such as a UPS system and generators.
Regarding this blackout, Mark Sheedy of the New York State Bridge Authority (NYSBA) said, "We didn't miss a beat, and we didn't lose a dollar here." (Toll Road News, 2003)
Another example of the need for emergency generators was during Superstorm Sandy that affected the New York/New Jersey metropolitan area. Electricity was knocked out by the storm, but emergency generators were brought on line quickly to bring tolling to resume operations.
The financial impact of these types of rare catastrophic failures may be great, but most tolling sites will never encounter such events. In addition, if a facility typically witnesses low traffic volumes and/or low toll rates, then the revenue lost even in a long-term outage may not justify the cost of installing an emergency power source. These sites should appraised to determine if a momentary loss of tolling revenue warrants a small battery backup system or none at all.
Many factors must be considered when designing a tolling system, such as whether the system uses open road tolling, managed lanes, or traditional tolling. Justification for large-scale emergency power sources should be evaluated on per site and per project basis. If the cost of designing, procuring, installing, and maintaining such a system greatly outweighs the financial impact of the potential lost revenue, then long-term emergency power supply may not be warranted.