Business Segments

We report financial and descriptive information about our reportable operating segments on a basis consistent with that used internally for evaluating segment performance and allocating resources to segments. We evaluate performance primarily on operating income.

We charge management fees and other corporate service fees to our reporting segments based on the benefits received or an overhead allocation basis. Shared support functions include information technology, legal, financial services, revenue management, and other company-wide services. Corporate represents residual operating expenses of the holding company that are not attributable to any segment and remain unallocated. It also represents certain items that are permitted to be excluded from Adjusted EBITDA. Corporate identifiable assets primarily consist of cash and cash equivalents, restricted amounts held in escrow, information technology assets, and deferred debt issuance costs. Intersegment revenue relates to transportation services between our segments.

We considered the disclosure requirements for revenue disaggregation guidance in ASC Topic 606 and noted that our segments disaggregate our revenues based on geographic and time-based factors as our Regional Transportation segment carriers operate in a smaller geographic footprint and have a shorter length of haul as compared to our YRC Freight segment.

Revenue from foreign sources totaled $104.1 million, $99.3 million, and $101.0 million for the years ended December 31, 2018, 2017, and 2016, respectively, and is mainly derived from Canada and, to a lesser extent, Mexico. Long-lived assets located in foreign countries totaled $6.5 million, $5.3 million and $5.2 million at December 31, 2018, 2017, and 2016, respectively.

The following table summarizes our operations by business segment:



(in millions)	YRC Freight			Regional Transportation			Corporate/Eliminations			Consolidated
2018
External revenue	$	3,197.3		$	1,895.0		$	(0.3	)	$	5,092.0
Operating income (loss)	85.0			70.7			(12.8		)	142.9
Identifiable assets	973.6			626.4			17.1			1,617.1
Acquisition of property and equipment	(76.5		)	(62.9		)	(6.0		)	(145.4		)
Proceeds from disposal of property and equipment	35.8			0.6			—			36.4
Depreciation and amortization	82.2			65.0			0.5			147.7
2017
External revenue	$	3,067.9		$	1,823.4		$	(0.3	)	$	4,891.0
Operating income (loss)^(a)	60.7			67.9			(9.6		)	119.0
Identifiable assets	1,042.1			607.4			(64.0		)	1,585.5
Acquisition of property and equipment	(66.6		)	(36.6		)	(0.1		)	(103.3		)
Proceeds from disposal of property and equipment	8.1			0.7			—			8.8
Depreciation and amortization	84.8			62.9			—			147.7
2016
External revenue	$	2,958.9		$	1,739.3		$	(0.7	)	$	4,697.5
Operating income (loss)^(a)	71.8			81.3			(8.6		)	144.5
Identifiable assets	1,208.7			642.9			(81.6		)	1,770.0
Acquisition of property and equipment	(73.2		)	(27.4		)	—			(100.6		)
Proceeds from disposal of property and equipment	31.3			3.8			—			35.1
Depreciation and amortization	90.3			69.5			—			159.8


(a)	Due to the adoption of ASU 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost,

“Operating income (loss)” for prior years have been updated to reflect the reclassification of pension expense