PROPERTY AND EQUIPMENT

12 Months Ended

Dec. 31, 2016

Property, Plant and Equipment [Abstract]

PROPERTY AND EQUIPMENT

Property and equipment includes land, buildings and improvements, machinery and equipment, roads and other items.

Carrying Value of Property and Equipment and Estimated Service Lives

DOLLAR AMOUNTS IN MILLIONS
	RANGE OF LIVES	DECEMBER 31, 2016			DECEMBER 31, 2015
Property and equipment, at cost:
Land	N/A	$	90		$	99
Buildings and improvements	15-35	789			791
Machinery and equipment	5-25	3,022			2,811
Roads	10-25	773			624
Other	3-10	194			195
Total cost		4,868			4,520
Allowance for depreciation and amortization		(3,306		)	(3,287		)
Property and equipment, net		$	1,562		$	1,233

SERVICE LIVES AND DEPRECIATION

In general, additions are classified into components, each with its own estimated useful life as determined at the time of purchase. Buildings and improvements for property and equipment have estimated lives that are generally at either the high end or low end of the range from 15 years to 35 years, depending on the type and performance of construction.

Depreciation expense, excluding discontinued operations, was:

• $198 million in 2016,

• $160 million in 2015 and

• $178 million in 2014.