Property, plant and equipment is recorded at historical cost less accumulated depreciation, which is calculated using the straight-line method over the estimated useful lives of the related assets, as follows (in thousands):


	December 31,				Estimated Useful Lives
	2022		2021
Vehicles	$	42,294	$	40,103	3-5 years
Computer equipment and software	74,459		83,479		3-5 years
Leasehold improvements	25,041		30,087		2-15 years
Office furniture, fixtures and equipment	12,754		22,327		2-7 years


Construction in process	18,446		11,089
Property, plant and equipment, gross	172,994		187,085
Accumulated depreciation and amortization	(111,358)		(131,637)
Property, plant and equipment, net	$	61,636	$	55,448

Property plant and equipment includes approximately $19.8 million and $16.5 million of assets under finance lease obligations, net of accumulated amortization of $23.3 million and $24.5 million at December 31, 2022 and 2021, respectively. Depreciation and amortization expense on all property plant and equipment was $17.5 million, $16.5 million and $20.2 million for the years ended December 31, 2022, 2021 and 2020, respectively. The Company recorded an impairment expense on its internal-use software of $1.8 million during the year ended December 31, 2022 and was included in depreciation and amortization expense. Amortization expense relates to assets under finance leases as included in depreciation and amortization expense.