Seek high yielding freight from targeted industries, customers, regions, and lanes that improves our overall network density and diversifies our customer and freight mix. We believe that by focusing our sales resources on targeted regions and lanes with emphasis on cross-border or international moves and a north - south direction, we can improve our lane density and equipment utilization, increase our average revenue per mile, and control our average cost per mile. Each piece of business has rate and productivity goals that are designed to improve our yield management. We believe that by increasing the business we do with less cyclical shippers, our ability to improve rate per mile increases.
Focus on asset productivity.
Our primary productivity measure is revenue per tractor per week. Within revenue per tractor we examine rates, non-revenue miles, and loaded miles per tractor. We actively analyze customers and freight movements in an effort to enhance the revenue production of our tractors. We also attempt to concentrate our equipment in defined operating lanes to create more predictable movements, reduce non-revenue miles, and shorten turn times between loads.
Operate a modern fleet to reduce maintenance costs and improve safety and driver retention.
We believe that updating our tractor fleet has produced several benefits, including enhanced safety, driver recruitment, and driver retention. We have taken an important step toward modernizing our fleet. We shortened the replacement cycle for our tractors from four years to three years. This trade policy has allowed us to recognize significant benefits over the past few years because maintenance and tire expenses increase significantly for tractors beyond the third year of operation, as wear and tear increases and some warranties expire.
Continue our emphasis on service, safety, and technology.
We offer just-in-time, time-definite and other premium transportation services to meet the expectations of our service-oriented customers. We believe that targeting premium service freight permits us to obtain higher rates, build long-term, service-based customer relationships, and avoid competition from railroad, intermodal, and trucking companies that compete primarily on the basis of price. We believe our recent safety record has been among the best in our industry. We have made significant investments in technologies that are intended to reduce costs, afford a competitive advantage with service-sensitive customers, be environmentally friendly, and promote economies of scale. Examples of these technologies are Qualcomm satellite-based tracking and communications systems, our proprietary CelaTrac system that enables customers to track shipments and access other information via the Internet, and document imaging.
Maintain our leading position in cross-border truckload shipments.
While offering diversified, nationwide transportation services in the U.S. We believe our strategically located terminals and experience with the languages, cultures, and border crossing requirements of all three North American countries provide us with competitive advantages in the international trucking marketplace. As a result of these advantages, we believe we are the industry leader in cross-border truckload transportation between North American countries. These cross-border shipments, which comprised 46% of our revenue in fiscal 2012, are balanced by a strong and growing business with domestic freight from service-sensitive customers.
Seeking strategic acquisitions to broaden our existing domestic operations.
We have made eighteen trucking company acquisitions since 2002 and continue to evaluate acquisition candidates. Our current acquisition strategy is focused on broadening our domestic operations through the addition of carriers that improve our lane density, customer diversity, and service offerings.