If the 133,220 railcars owned by Berkshire's Marmon Industries were put into a single train, its locomotive would be in Omaha and its caboose in Portland, Maine.
At the end of 2015, 97 percent of the cars were leased, with 7 percent of them carrying crude oil. The most common cargo is chemicals and refined petroleum products.
Buffett would be "delighted" to use some of Berkshire's cash to buy its own shares if the company's stock price falls below 120 percent of its book value.
At the end of 2015, the book value was $155,501, making the buyback price $186,601. That's 5.8 percent below the latest pershare price of $198,190.50.
The book value grew by $15.4 billion in 2015, so it has been catching up to the slumping stock price. Buffett said Berkshire's "intrinsic value far exceeds its book value" because the increase in value of its operating businesses, especially its insurance companies, isn't recognized by the accounting methods used to calculate book value.
If Berkshire buys its shares, he said, the value of remaining shareholders' stock would increase.
Berkshire's dozens of small non-insurance businesses earned $5.7 billion last year, up from $5.1 billion in 2014.
Berkshire invested $16 billion in property, plant and equipment last year, 86 percent of it in the United States. Of the total, $1.6 billion was invested by BNSF Railway and Berkshire Hathaway Energy.
Berkshire Hathaway Energy has invested $16 billion in renewable energy and now owns 7 percent of the country's wind-generating capacity (six times the share owned by the nearest other utility) and 6 percent of U.S. solar-generating capacity.
Berkshire's largest unrecorded wealth lies in its insurance companies, which hold $88 billion in "float" while waiting for claims. Over 13 years, the companies have made $26 billion by receiving more premium dollars than they pay out for claims.