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


(in millions)	Useful Lives	December 31, 2024		December 31, 2023

Land		$	69	$	72
Buildings and equipment	Up to 30 years	4,377		4,465
Wireless communications systems	Up to 20 years	65,778		65,628
Leasehold improvements	Up to 10 years	2,588		2,489
Capitalized software	Up to 8 years	18,566		22,573
Leased wireless devices	Up to 16 months	145		400
Construction in progress	N/A	3,377		3,286
Accumulated depreciation and amortization		(56,367)		(58,481)

Property and equipment, net		$	38,533	$	40,432

Total depreciation expense relating to property and equipment and financing lease right-of-use assets was $12.1 billion, $12.0 billion and $12.7 billion for the years ended December 31, 2024, 2023 and 2022, respectively. These amounts include depreciation expense related to leased wireless devices of $54 million, $170 million and $1.1 billion for the years ended December 31, 2024, 2023 and 2022, respectively.

We capitalize interest associated with the acquisition or construction of certain property and equipment and spectrum intangible assets. We recognized capitalized interest of $34 million, $104 million and $61 million for the years ended December 31, 2024, 2023 and 2022, 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, 2024		Year Ended December 31, 2023

Asset retirement obligations, beginning of year	$	1,716	$	1,852

Liabilities incurred	21		28
Liabilities settled	(307)		(399)
Accretion expense	69		71
Changes in estimated cash flows	36		164


Asset retirement obligations, end of period	$	1,535	$	1,716

Classified on the consolidated balance sheets as:

Other current liabilities	$	109	$	133
Other long-term liabilities	1,426		1,583

The corresponding assets, net of accumulated depreciation, related to asset retirement obligations were $423 million and $462 million as of December 31, 2024 and 2023, respectively.