Shares of J.B. Hunt Transport ( JBHT) were up slightly Friday after the company's second-quarter profit nearly doubled due to a strong performance from its trucking segment.The Lowell, Ark.-based transportation company said after the bell Thursday that net income rose to $45.6 million, or 55 cents a share, from $25.1 million, or 31 cents a share, in the same period last year. A Thomson First Call consensus analyst estimate had called for earnings of 45 cents a share. Sales rose to $679 million from $600 million, beating the consensus estimate of $649.84 million. The company said that of its three businesses, its trucking segment was the most profitable this quarter, as claims were lower than expected and rate yields improved as the loaded rate-per-mile increased. However, the company indicated that there was a difficulty expanding the driver base industry wide and thus any increase in capacity would be difficult. "Even though we expect to be able to sustain the improvements in margins we have achieved, growth in the truckload industry is at a virtual standstill until additional truck drivers are attracted to the industry," the company said in a statement. Shares of J.B. Hunt Transport are recently up 25 cents to $36.15.