Every day, tens of thousands of cargo tank trucks transport hazardous materials classified as flammable liquids (primarily gasoline and fuel oil) for sale in the United States. This involves some safety risk because of the volatile nature of flammable liquids, the volume of liquid transported (up to 9,200 gallons per truck), and the numbers of trucks and passenger vehicles on the road. Tank trucks that carry flammable liquids have three main components—the truck, the trailer, and the cargo tank. The tank may be divided into several compartments—usually four or five—allowing the truck to carry different petroleum products in a single trip, such as different grades of gasoline and diesel fuel. Although the design of cargo tank trucks can vary depending on the model and manufacturer, the components in figure 1 are common features. The rule proposed by PHMSA in January 2011 would require that flammable liquids be eliminated from bottom loading and unloading lines, such as by purging the bottom lines of product, or that bottom lines be protected with approved bottom protection devices. The rule would apply to cargo tank trucks that typically transport gasoline, diesel, and fuel oil from distribution terminals—of which there are nearly 400 nationwide—to retail outlets or gas stations (see fig. 2). In the 1980s, to address volatile organic compound emission reduction requirements, as well as worker safety issues, the petroleum industry changed cargo tank-loading procedures from loading through the manhole covers on the top of the truck to loading through the bottom lines. Prior to this change, the bottom lines were used for unloading only and therefore generally did not contain more than a residual amount of flammable liquids during transport. In using bottom lines for loading, because the lines are at the lowest point on the truck, they do not drain into the main tanks but contain fuel. Bottom lines containing fuel are referred to as “wetlines.” Wetline incidents result from collisions involving tank trucks that lead to the release of flammable liquid from wetlines. Such incidents range from easily contained spills to catastrophic situations. Carriers that transport hazardous materials, including flammable liquids like gasoline, are required to report incidents involving the release of hazmat to PHMSA. Carriers, for example, must submit an electronic or paper incident reporting form within 30 days of the incident. This form is designed to provide information about the vehicle and container involved in the incident, the component of the container that failed, the type and quantity of product released, and, if applicable, fatalities, injuries, and the dollar value of significant damages associated with the incidents.includes a space for carriers to write a descriptive narrative of the incident. Information from these forms appears in PHMSA’s publicly The form also available web-based incident database.database for its safety oversight work, including regulatory efforts. According to PHMSA, it uses the While most wetline incidents identified by PHMSA did not result in fires, spilled flammable liquid can ignite and create the potential for fatalities as well as increased property and environmental damages. Incidents may be the result of a tank truck striking a stationary object or a moving passenger vehicle striking the tank truck. Figure 3 shows examples of two types of wetline incidents. PHMSA is responsible for regulating the safe and secure transportation of hazardous materials to reduce the risks to people and the environment. In 1989 and 1990, PHMSA’s predecessor, the Research and Special Programs Administration, promulgated final rules that prohibited external product piping, such as bottom lines, from retaining hazardous liquids unless the cargo tank truck is equipped with bottom damage protection devices. Citing concerns about the potential costs of modifying fuel terminal operations, the lack of data on incidents, and the lack of information on possible alternatives to empty wetlines after bottom loading, the Research and Special Programs Administration exempted tanks transporting gasoline and other flammable liquids from the regulation. Thus, the resulting regulations, in general, pertain to certain poisonous liquids, oxidizer liquid, liquid organic peroxide, or corrosive liquids, but not to gasoline. The 1997 Yonkers incident drew attention to the safety risks of wetlines because it involved a fatality as well as unusually high damages. Specifically, its destruction of a highway overpass resulted in severe property damage, and the incident’s location in a congested area led to severe economic costs. Following NTSB’s recommendation that DOT prohibit transport of hazardous materials in wetlines, Research and Special Programs Administration and later PHMSA) submitted a draft proposed rule to the Office of Management and Budget (OMB) to address the issue in 2000 and later issued a proposed rule in 2004. PHMSA withdrew its 2004 proposed rulemaking in 2006 because it concluded that the benefits of the rule would not justify the costs. PHMSA proposed another wetline rule in 2011. Figure 4 shows the timeline of key events and major regulatory efforts to address wetline risks. The NTSB considers the practice of transporting flammable liquids in wetlines to be an unsafe practice and contends that incidents similar to the Yonkers incident are likely to occur in the future. 76 Fed. Reg. 4847, 4848 (Jan. 27, 2011). Section 33015 of MAP-21 prohibits DOT from issuing a wetlines final rule prior to either the completion of GAO’s mandated study or until July 2014, whichever is earlier, unless DOT determines that a risk to public safety, property, or the environment is present or an imminent hazard exists and that the regulations will address the risk or hazard. PHMSA’s incident data do not reliably capture the risks and consequences of wetline incidents because these incidents are not specifically identified in its database, and PHMSA’s incident data also contain inaccuracies. Although PHMSA requires reporting of hazmat incidents through incident reporting forms, it does not require carriers to explicitly state on the form whether the incident is wetline-related. Consequently, to identify wetline incidents, PHMSA officials must review carrier-reported narratives and other information, a review that is resource-intensive. Moreover, this review may not result in an accurate accounting of the number and consequences of wetline incidents because the information does not always clearly indicate whether the incident is wetline-related and because of inaccuracies and omissions in the data. PHMSA has made efforts to improve its data, such as implementing quality checks, but this does not affect how wetline incidents are reported, and errors remain. This limits the usefulness of these data as supporting information for PHMSA’s wetline regulatory analysis. PHMSA’s hazmat incident database does not specifically code incidents as wetline-related because its incident reporting form does not require carriers to explicitly report whether an incident is wetline-related. Consequently, it is not possible to retrieve a list of wetline incidents through PHMSA’s database. To identify wetline incidents, PHMSA staff must analyze incident narratives and other carrier-reported information for characteristics that are indicative of wetline incidents.identifying these incidents resource-intensive and somewhat subjective, since the determination of which incidents are wetline-related is not always based on complete information, as incident data may be unclear or missing. OMB guidance states that agencies should develop a process for reviewing information quality as part of information resources management, including when collecting and maintaining the information to be used for regulatory analysis, which is one of PHMSA’s uses for its incident data. Annually, PHMSA receives reports of about 15,000 to 20,000 hazmat incidents, and the percentage of these incidents that PHMSA identified as wetline-related is relatively small. To support PHMSA’s 2011 cost-benefit analysis, PHMSA officials said that a team spent months reviewing incident data to identify wetline incidents and, as of January 2011, identified 172 wetline incidents occurring over the 10-year period from January 1999 through December 2008.the January 2011 proposed rule and related cost-benefit analysis. According to PHMSA’s updated March 2012 draft cost-benefit analysis, after commenters in the wetline rulemaking docket questioned whether some of these incidents should have been identified as wetline incidents, PHMSA reexamined the 172 incidents it originally identified and updated the analysis to include incidents through March 2011. This led PHMSA to a provisional figure of 132 wetline incidents, which PHMSA used in its These incidents were used in updated 2012 draft cost-benefit analysis.issued a final rule on this subject, information in either the 2011 or draft 2012 analysis is subject to change. To identify wetline incidents for both the 2011 and 2012 reviews, PHMSA officials said they conducted a broad search of cargo tank truck incidents in the database and then reviewed incident reports’ narrative descriptions. If a description was insufficient to make a determination, officials reviewed the content of other fields in the incident’s database entry such as component failure information, packaging identification, the amount and type of hazardous material released, and location of the vehicle at the time of the accident. PHMSA officials said their incident database provided sufficient information about incidents to make a judgment about each incident. However, the amount of time, staff, and specialized knowledge required for this process was more extensive than if PHMSA required carriers to identify whether incidents are wetline-related on the incident reporting forms. Officials also stated that, since their method of identifying wetline incidents by reviewing narrative descriptions required substantial resources, the agency was not able to direct additional resources to follow up with carriers to clarify missing or unclear data as part of the review to identify wetline incidents, except in cases involving fatalities. In identifying consequences of wetline incidents, PHMSA has little information besides what is provided by the carriers.