Safety regulations on tank cars will likely keep demand strong. Monthly rates for tank cars have increased. Bloomberg News A shortage of railcars bedeviling farmers, auto makers and oil drillers has become a windfall for some railcar manufacturers, lessors and finance companies. “There’s strong demand for a broad base of car types and there’s not enough inventory,” said David Nahass, senior vice president at Railroad Financial Corp., a Chicago-based investment adviser. “As an operator or lessor in this environment, this is what you pray for.” Monthly rates for tank cars, which transport liquids such as crude oil, have increased to $1,500 to $2,000 a car from about $500 in early 2011, before hydraulic fracturing ramped up in North Dakota’s Bakken Shale oil field. Cars that haul sand for fracking are leasing for about $650 a month, up nearly 50% from the end of last year, according to leasing-industry analysts. […]