Property



	Estimated Useful Lives in Years	December 31, 2018			December 31, 2017
Land		$	1,349		$	1,647
Buildings and improvements	5-40	9,173			7,471
Machinery and equipment	3-27	26,453			23,915
Special tools	1-13	23,828			21,113
Construction in progress		4,680			6,188
Total property		65,483			60,334
Less: accumulated depreciation		(26,725		)	(24,081		)
Total property, net		$	38,758		$	36,253

The amount of capitalized software included in Property, net was $1.1 billion and $1.2 billion at December 31, 2018 and 2017. The amount of interest capitalized and excluded from Automotive interest expense related to Property, net was insignificant in the years ended December 31, 2018, 2017 and 2016.



	Years Ended December 31,
	2018		2017		2016
Depreciation and amortization expense	$	5,347	$	4,966	$	4,622
Impairment charges	$	466	$	199	$	68
Capitalized software amortization expense(a)	$	424	$	459	$	458

__________


(a)	Included in depreciation and amortization expense.