The components of property and equipment, excluding amounts transferred to held for sale, were as follows:


(in millions)	Useful Lives	December 31, 2023		December 31, 2022

Land		$	72	$	109
Buildings and equipment	Up to 30 years	4,465		4,659
Wireless communications systems	Up to 20 years	65,628		61,738
Leasehold improvements	Up to 10 years	2,489		2,326
Capitalized software	Up to 10 years	22,573		20,342
Leased wireless devices	Up to 16 months	400		1,415
Construction in progress	N/A	3,286		4,599
Accumulated depreciation and amortization		(58,481)		(53,102)

Property and equipment, net		$	40,432	$	42,086

Total depreciation expense relating to property and equipment and financing lease right-of-use assets was $12.0 billion, $12.7 billion and $15.2 billion for the years ended December 31, 2023, 2022 and 2021, respectively. These amounts include depreciation expense related to leased wireless devices of $170 million, $1.1 billion and $3.1 billion for the years ended December 31, 2023, 2022 and 2021, respectively.

We capitalize interest associated with the acquisition or construction of certain property and equipment and spectrum intangible assets. We recognized capitalized interest of $104 million, $61 million and $210 million for the years ended December 31, 2023, 2022 and 2021, respectively.

Asset retirement obligations are primarily for certain legal obligations to remediate leased property on which our network infrastructure and administrative assets are located.

Activity in our asset retirement obligations was as follows:


(in millions)	Year Ended December 31, 2023		Year Ended December 31, 2022

Asset retirement obligations, beginning of year	$	1,852	$	1,899

Liabilities incurred	28		10
Liabilities settled	(399)		(379)
Accretion expense	71		65
Changes in estimated cash flows	164		292
Transfers to held for sale	—		(35)

Asset retirement obligations, end of period	$	1,716	$	1,852

Classified on the consolidated balance sheets as:

Other current liabilities	$	133	$	267
Other long-term liabilities	1,583		1,585

The corresponding assets, net of accumulated depreciation and excluding amounts transferred to held for sale, related to asset retirement obligations were $462 million and $546 million as of December 31, 2023 and 2022, respectively.

Previously, the operation of the legacy Sprint CDMA and LTE wireless networks was supported by the legacy Sprint Wireline network. During the second quarter of 2022, we retired the legacy Sprint CDMA network and began the orderly shut-down of the LTE network. We determined that the retirement of the legacy Sprint CDMA and LTE wireless networks triggered the need to assess the Wireline long-lived assets for impairment, as these assets no longer supported our wireless network and the

associated customers and cash flows in a significant manner. The results of this assessment indicated that certain Wireline long-lived assets were impaired. See Note 14 – Wireline for further information.