PROPERTY AND EQUIPMENT

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

PROPERTY AND EQUIPMENT

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, 2018			DECEMBER 31, 2017
Property and equipment, at cost:
Land	N/A	$	87		$	88
Buildings and improvements	15-40	942			867
Machinery and equipment	5-25	3,240			3,037
Roads	10-35	785			782
Other	3-10	179			182
Total cost		5,233			4,956
Accumulated depreciation and amortization		(3,376		)	(3,338		)
Property and equipment, net		$	1,857		$	1,618

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 low end or high end of the range from 15 years to 40 years, depending on the type and performance of construction.

Depreciation expense was:

• $197 million in 2018,

• $206 million in 2017 and

• $198 million in 2016 (excluding discontinued operations).