Certain acronyms and terms used throughout this Annual Report on Form 10-K are specific to our company, commonly used in our industry, or are otherwise frequently used throughout our document. Definitions for these acronyms and terms are provided in the "Glossary of Terms," available in the front of this document.

Swift is a multi-faceted transportation services company, operating one of the largest fleets of truckload equipment in North America from over 40 terminals near key freight centers and traffic lanes. We principally operate in short- to medium-haul traffic lanes around our terminals and dedicated customer locations. During 2015 , our consolidated average operational truck count was 17,915 , which covered 2.2 billion miles for shippers throughout North America, contributing to consolidated operating revenue of $4.2 billion and consolidated operating income of $370.1 million . As of December 31, 2015 , our fleet was comprised of 15,211 company tractors and 4,653 owner-operator tractors, as well as 65,233 trailers and 9,150 intermodal containers. Our customers have the opportunity to "one-stop-shop" for their truckload transportation needs with our extensive suite of service offerings, which include line-haul services, dedicated customer contracts, temperature-controlled units, intermodal freight solutions, cross-border United States/Mexico and United States/Canada freight, flatbed hauling, freight brokerage and logistics, and others.

Jerry Moyes, along with his father and brother, founded Swift Transportation Co., Inc. ("Swift Transportation") in 1966 with only one truck. In 1990, Swift Transportation went public on the NASDAQ stock market.

Central is a premium service truckload carrier specializing in temperature-controlled freight transportation and was a large provider of temperature-controlled truckload services in the United States. With the addition of Central to its dedicated temperature-controlled business, Swift is one of the largest temperature-controlled truckload providers in the United States. Our accounting treatment of the Central Acquisition and other details are discussed in Note 1 in Part II, Item 8, Financial Statements and Supplementary Data.

Truckload carriers represent the largest part of the transportation supply chain for most retail and manufactured goods in North America and typically transport a full trailer (or container) of freight for a single customer from origin to destination without intermediate sorting and handling. Generally, the truckload industry is compensated based on miles, whereas the LTL industry is compensated based on package size and/or weight. Overall, the United States trucking industry is large, fragmented, and highly competitive. We compete with thousands of truckload carriers, most of whom operate much smaller fleets than we do. To a lesser extent, our intermodal services, as well as our freight brokerage and logistics business, compete with railroads, LTL carriers, logistics providers, and other transportation companies.

Our industry has encountered the following major economic cycles since 2000:

The principal means of competition in our industry are customer service, capacity, and price. In times of strong freight demand, customer service and capacity become increasingly important, and in times of weak freight demand, pricing becomes increasingly important. Most truckload contracts (other than dedicated contracts) do not guarantee truck availability or load levels. Pricing is influenced by supply and demand.

The trucking industry faces the following primary challenges, which we believe we are well-positioned to address, as discussed under "Our Competitive Strengths" and "Company Strategy," below:

Our mission is to attract and retain customers by providing best in class transportation solutions and fostering a profitable, disciplined culture of safety, service and trust.

We aspire to achieve the themes of our mission and vision and believe our competitive strengths and strategies will enable us to attain our desired level of service to customers and results for our shareholders. We believe the following competitive strengths provide a solid platform for pursuing our goals and strategies:

Our key financial goals include improving our asset utilization, controlling costs, growing Adjusted EPS (defined in "Non-GAAP Financial Measures" under Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations), improving return on net assets, and generating cash flow to reinvest in our business, repay debt and return capital to our stockholders. We align our company focus to attain these goals by implementing the following strategies, which we believe also serve to minimize the impact of challenges currently faced in the trucking industry.

We believe that by achieving profitable revenue growth, improving asset utilization, continuing to control costs, and streamlining our processes, we will be able to grow our Adjusted EPS and our return on net assets, while generating free cash flow to reinvest in our business, repay debt, reduce our leverage ratio and return capital to our stockholders. These goals are in part dependent on continued improvement in industry-wide truckload volumes and pricing. Although we expect the economic environment and capacity constraints in our industry to support achievement of our goals, we have limited ability to affect industry volumes and pricing and cannot provide assurance that this environment will sustain. Nevertheless, we believe our competitive strengths and the current supply and demand environment in the truckload industry are aligned to support the achievement of our goals through the strategies outlined above.

No customer, other than Wal-Mart, accounted for more than 10% of our operating revenue during 2015 , 2014 or 2013 .

(1) Excludes 4,653 owner-operator tractors.

We typically purchase or lease tractors and trailers manufactured to our specifications. We follow a comprehensive maintenance program designed to reduce downtime and enhance the resale value of our equipment. We have major maintenance facilities in the following locations:

In addition to these maintenance facilities, we perform routine servicing and maintenance of our revenue equipment at most of our regional terminal facilities, in an effort to avoid costly on-road repairs and deadhead miles. The contracts governing our equipment purchases typically contain specifications of equipment, projected delivery dates, warranty terms, and trade or return conditions, and are cancelable upon 60 to 90 days' notice without penalty.

In 2015, we accelerated our tractor trade-in cycle from an average of 48 to 72 months to an average of 36 to 48 months, depending on equipment type and usage. We believe that our newer equipment has enhanced features, which tend to lower the overall life cycle costs by reducing safety-related expenses, lowering repair and maintenance expenses, improving fuel economy and improving driver satisfaction. In 2016 and beyond, we will continue to monitor the appropriateness of this shorter tractor trade-in cycle against the lower capital expenditure and financing costs of a longer tractor trade-in cycle, based on current and future business needs.

We equip virtually all of our trucks with certain OmniTRACS ^tm technologies that enhance communication between the regional terminals and corporate headquarters, as well as the added benefits of ELDs, text-to-voice messaging, and turn-by-turn directions designed specifically for our industry. This allows us to alter driver routes rapidly, in case of urgent customer requests, adverse weather conditions, road closures or other potential delays. It also enables our drivers to timely communicate route status or the need for emergency repairs. These technologies have afforded us additional productivity, improved safety, and increased customer and driver satisfaction.

We reduce costs through programs that manage equipment maintenance, select fuel purchasing locations in our nationwide network of terminals and approved truck stops, and inform us of inefficient or undesirable driving behaviors that are monitored and reported through electronic engine sensors and cameras. We believe our technologies and systems are superior to those employed by most of our smaller competitors.

Our trailers and containers are equipped with tracking devices that monitor locations of empty and loaded equipment via satellite. Notification is sent to us if a unit is moved outside of the electronic geofence encasing on each piece of equipment. This enables us to identify unused or hijacked units, enhance our ability to charge for units detained by customers, and reduce theft.

The strength of our company is our people, working together with common goals. There were approximately 20,800 full-time employees in our total headcount of approximately 21,000 employees as of December 31, 2015 , which was comprised of:

As of December 31, 2015 , our 819 Trans-Mex drivers in Mexico were our only employees represented by a union.

We have established eight driver academies across the United States. Our academies are strategically located in areas where external driver-training organizations were lacking. In other areas of the United States, we have contracted with driver-training schools, which are managed by third parties. There are certain minimum qualifications for candidates to be accepted into the

academy, including passing the DOT physical examination and drug/alcohol screening. Students are required to complete three weeks of instructor-led study/training and then spend a minimum of 200 behind-the-wheel hours, driving with an experienced trainer.

In order to attract and retain qualified drivers and promote safe operations, we purchase high quality tractors equipped with optional comfort and safety features. We base our drivers at terminals and monitor each driver’s location in order to schedule routing for our drivers so they can return home regularly. The majority of company drivers are compensated based on industry standard dispatched miles, loading/unloading, and number of stops or deliveries, plus bonuses. The driver’s base pay per mile increases with the driver’s length of experience. Our driver ranking system measures safety, compliance, customer service, and number of miles driven. Higher rankings provide drivers with additional benefits and/or privileges, such as special recognition, the ability to self-select freight, and the opportunity for increased pay.

Upon enrollment eligibility, drivers employed by us may participate in company-sponsored health, life and dental insurance plans and participate in our 401(k) and employee stock purchase plans.

In addition to Swift-employed company drivers, we enter into contractor agreements with third parties who own and operate tractors (or hire their own drivers to operate the tractors) that service our customers. We pay these owner-operators for their services, based on a contracted rate per mile. By operating safely and productively, owner-operators can improve their own profitability and ours. Owner-operators are responsible for most costs incurred for owning and operating their tractors. For convenience, we offer owner-operators maintenance services at our in-house shops and fuel at our terminals at competitive and attractive prices. As of December 31, 2015 , owner-operators comprised approximately 23% of our total fleet, as measured by tractor count.

We offer tractor financing to independent owner-operators through our financing subsidiaries. Our financing subsidiaries generally lease premium equipment from the original equipment manufacturers and sublease the equipment to owner-operators. The owner-operators are qualified for financing, based on their driving and safety records. In the event of default, our financing subsidiaries have the option to repossess the tractor and sublease it to a replacement owner-operator.

We take pride in our safety-oriented culture and maintain an active safety and loss-prevention program, which is led by regional safety management personnel at each of our terminals. We also equip our tractors with many safety features, such as roll-over stability devices and critical-event recorders, to help prevent, or reduce the severity of, accidents. We self-insure for a significant portion of our claims exposure and related expenses. We currently carry six main types of insurance, which generally have the following self-insured retention amounts, maximum benefits per claim, and other limitations:

We insure certain casualty risks through our wholly-owned captive insurance subsidiaries, Mohave and Red Rock. Mohave and Red Rock provide reinsurance associated with a share of our automobile liability risk. In addition to insuring a proportionate share of our corporate casualty risk, Mohave provides reinsurance coverage to third-party insurance companies associated with our affiliated companies’ owner-operators.

While under dispatch and our operating authority, the owner-operators we contract with are covered by our liability coverage and self-insurance retention limits. However, each is responsible for physical damage to his or her own equipment, occupational accident coverage and liability exposure while the truck is used for non-company purposes. Additionally, fleet operators are responsible for any applicable workers’ compensation requirements for their employees.

We regulate the speed of our company tractors to a maximum of 62 miles per hour and for safety reasons have contractually agreed with owner-operators to limit their speed to 68 miles per hour. These adopted speed limits are below the limits established by statute in many states. We believe our adopted speed limits for company drivers reduce the frequency and severity of accidents, enhance fuel efficiency, and reduce maintenance expense, when compared to operating without our imposed speed limits. Substantially all of our company tractors are equipped with electronically-controlled engines that are set to limit the speed of the vehicle.

We actively manage our fuel purchasing network in an effort to maintain adequate fuel supplies and reduce our fuel costs. Additionally, we utilize a fuel surcharge program to pass a majority of increases in fuel costs to our customers. In 2015 , we purchased 17% of our fuel in bulk at 57 Swift and dedicated customer locations across the United States and Mexico. We purchased substantially all of the remainder through a network of retail truck stops with which we have negotiated volume purchasing discounts. The volumes we purchase at terminals and through the fuel network vary based on procurement costs and other factors. We seek to reduce our fuel costs by routing our drivers to truck stops when fuel prices at such stops are cheaper than the bulk rate paid for fuel at our terminals. We store fuel in underground storage tanks at two of our bulk fueling terminals and in above-ground storage tanks at our other bulk fueling terminals. We believe that we are sufficiently in compliance with applicable environmental laws and regulations relating to the storage and dispensing of fuel.

In the truckload industry, results of operations generally show a seasonal pattern. As customers ramp up for the year-end holiday season, the late third and fourth quarters have historically been our strongest volume quarters. As customers reduce shipments after the winter holiday season, the first quarter has historically been a lower volume quarter for us than the other three quarters. In recent years, the macro consumer buying patterns combined with shippers’ supply chain management, which historically contributed to the fourth quarter "peak" season, continued to evolve. As a result, our fourth quarter 2015 , 2014 and 2013 volumes were more evenly disbursed throughout the quarter rather than peaking early in the quarter. In the eastern and mid-western United States, and to a lesser extent in the western United States, during the winter season our equipment utilization typically declines and operating expenses generally increase, with fuel efficiency declining because of engine idling and severe weather sometimes creating higher accident frequency, increased claims, and more equipment repairs. Revenue may also be affected by holidays as a result of curtailed operations or vacation shutdowns, because our revenue is directly related to available working days of shippers. From time to time, we also suffer short-term impacts from severe weather and similar events, such as tornadoes, hurricanes, blizzards, ice storms, floods, fires, earthquakes, and explosions that could harm our results of operations or make our results of operations more volatile.

General — We have bulk fuel storage and fuel islands at many of our terminals, as well as vehicle maintenance, repair, and washing operations at some of our facilities, which exposes us to certain environmental risks. Soil and groundwater contamination have occurred at some of our facilities in prior years, for which we have been responsible for remediating the environmental contamination. Also, less than one percent of our total shipments contain hazardous materials, which are generally rated as low- to medium-risk. In the past, we have been responsible for the costs of clean-up of cargo and diesel fuel spills caused by traffic accidents or other events.

We have instituted programs to monitor and mitigate environmental risks and maintain compliance with applicable environmental laws dealing with the hauling, handling and disposal of hazardous materials, fuel spillage or seepage, emissions from our vehicles and facilities, engine-idling, discharge and retention of storm water, and other environmental matters. As part of our safety and risk management program, we periodically perform internal environmental reviews. We are a Charter Partner in the EPA’s SmartWay Transport Partnership, a voluntary program promoting energy efficiency and air quality. We believe that our operations are sufficiently in compliance with current laws and regulations and do not know of any existing environmental condition that would reasonably be expected to have a material adverse effect on our business or operating results.

If we are held responsible for the cleanup of any environmental incidents caused by our operations or business, or if we are found to be in violation of applicable laws or regulations, we could be subject to liabilities, including substantial fines or penalties or civil and criminal liability. We have paid penalties for spills and violations in the past.

Greenhouse Gas Emissions and Fuel Efficiency Standards — In 2008 the State of California's Air Resources Board ("ARB") approved the Heavy-Duty Vehicle GHG Emission Reduction Regulation in efforts to reduce GHG emissions from certain long-haul tractor-trailers that operate in California by requiring them to utilize technologies that improve fuel efficiency (regardless of where the vehicle is registered). The regulation required owners of long-haul tractors and 53-foot trailers to replace or retrofit their vehicles with aerodynamic technologies and low rolling resistance tires. The regulation also contained certain emissions and registration standards for refrigerated trailer operators.

Thereafter, the United States EPA and the National Highway Traffic Safety Administration ("NHTSA") began taking coordinated steps in support of a new generation of clean vehicles and engines through reduced GHG emissions and improved fuel efficiency at a national level.

In December 2013, California's ARB approved regulations to align its GHG emission standards and test procedures, as well as its tractor-trailer GHG regulation, with the federal Phase 1 GHG regulation.

Current and proposed GHG regulations could impact us by increasing the cost of new tractors, impairing productivity, and increasing our operating expenses.

Climate-change Proposals — Federal and state lawmakers are considering a variety of climate-change proposals related to carbon emissions and GHG emissions. The proposals could potentially limit carbon emissions for certain states and municipalities, which continue to restrict the location and amount of time that diesel-powered tractors (like ours) may idle.

Our operations are regulated and licensed by various federal, state and local government agencies in North America, including the DOT, the FMCSA, and the DHS, among others. Our company, as well as our drivers and contracted owner-operators, must comply with enacted governmental regulations regarding safety, equipment, environmental protection, and operating methods. Examples include regulation of equipment weight, equipment dimensions, fuel emissions, driver hours-of-service, driver eligibility requirements, on-board reporting of operations, and ergonomics. The following discussion presents recently enacted federal, state and local regulations that have an impact on our operations.

Since 2004 the hours-of-service rules allowed drivers to restart their duty-cycle clocks every 34 hours to begin a new work week. From July 2013 through December 2014, the FMCSA required that drivers include 1:00 a.m. to 5:00 a.m. on consecutive days for applying the restart, which was also capped at once per week, or 168 hours. On December 13, 2014, Congress passed the fiscal year 2015 Omnibus Appropriations bill, which temporarily suspended enforcement of the 1:00 to 5:00 am provision and the 168-hour rule until September 30, 2015. The restart provision was again suspended on December 18, 2015, when Congress passed the fiscal year 2016 Omnibus Appropriations bill.  All other provisions of the hours-of-service rules that went into effect on July 1, 2013 remained unchanged. A study on the effectiveness of the suspended restart provisions was recently completed. The FMCSA could move to reinstate these provisions or request that Congress remove the suspension.

Certain BASICs information was initially published and made available to carriers, as well as the general public. However, in December 2015, as part of the Fixing America's Surface Transportation ("FAST") Act, Congress mandated that the FMCSA remove all CSA scores from public view until a more comprehensive study regarding the effectiveness of BASICs improving truck safety can be completed. Swift scored within the acceptable level in the safety-related categories, based on our CSA rankings.

Implementation and effective dates are unclear, as there is currently no proposed rulemaking with respect to BASICs, leaving SafeStat the authoritative safety measurement system in effect. We currently have a satisfactory SafeStat DOT rating, which is the best available rating under the current safety rating scale.

The FMCSA estimates that the proposed rule would increase the number of carriers determined to be "unfit" by more than two and a half times.

General information about Swift is provided, free of charge, on our website, www.swifttrans.com . This website also includes our annual reports on Form 10-K with accompanying XBRL documents, quarterly reports on Form 10-Q with accompanying XBRL documents, current reports on Form 8-K, and amendments to those reports that are filed or furnished pursuant to Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as soon as reasonably practicable once the material is electronically filed or furnished to the SEC.