OPERATING SEGMENTS The Partnerships operations consist of four operating segments: (i) asphalt terminalling services, (ii) crude oil terminalling services, (iii) crude oil pipeline services and (iv) crude oil trucking services. ASPHALT TERMINALLING SERVICES  The Partnership provides liquid asphalt cement and residual fuel oil terminalling services at its 53 terminalling facilities located in 26 states. CRUDE OIL TERMINALLING SERVICES  The Partnership provides crude oil terminalling services at its terminalling facility located in Oklahoma. CRUDE OIL PIPELINE SERVICES  The Partnership owns and operates pipeline systems that gather crude oil purchased by its customers and transports it to refiners, to common carrier pipelines for ultimate delivery to refiners or to terminalling facilities owned by the Partnership and others. The Partnership refers to its pipeline system located in Oklahoma and the Texas Panhandle as the Mid-Continent pipeline system. The Partnership previously owned and operated the East Texas pipeline system, which is located in Texas. On April 18, 2017, the Partnership sold the East Texas pipeline system. See Note 8 for additional information. Crude oil marketing revenues consist of sales proceeds recognized for the sale of crude oil to third-party customers. Revenue for the sale of crude oil is recognized when title to the crude oil transfers to the customer and is based on contractual prices for the sale of crude oil. CRUDE OIL TRUCKING SERVICES  The Partnership uses its owned and leased tanker trucks to gather crude oil for its customers at remote wellhead locations generally not covered by pipeline and gathering systems and to transport the crude oil to aggregation points and terminalling facilities located along pipeline gathering and transportation systems. On April 24, 2018, the Partnership sold the producer field services business. As a result of the sale of the producer field services business, the Partnership changed the name of this operating segment to crude oil trucking services during the second quarter of 2018. See Note 8 for additional information. The Partnerships management evaluates performance based upon segment operating margin, which includes revenues from related parties and external customers and operating expense excluding depreciation and amortization. The non-GAAP measure of operating margin (in the aggregate and by segment) is presented in the following table. The Partnership computes the components of operating margin by using amounts that are determined in accordance with GAAP. The Partnership accounts for intersegment product sales as if the sales were to third parties, that is, at current market prices. A reconciliation of operating margin to income before income taxes, which is its nearest comparable GAAP financial measure, is included in the following table. The Partnership believes that investors benefit from having access to the same financial measures being utilized by management. Operating margin is an important measure of the economic performance of the Partnerships core operations. This measure forms the basis of the Partnerships internal financial reporting and is used by its management in deciding how to allocate capital resources among segments. Income before income taxes, alternatively, includes expense items, such as depreciation and amortization, general and administrative expenses and interest expense, which management does not consider when evaluating the core profitability of the Partnerships operations. The following table reflects certain financial data for each segment for the periods indicated (in thousands): Year ended December 31, 2016 2017 2018 Asphalt Terminalling Services Service revenue: Third-party revenue $ 75,655 $ 57,486 $ 26,108 Related-party revenue 11,762 56,378 21,686 Lease revenue: Third-party revenue   41,319 Related-party revenue   25,961 Product sales revenue: Related-party revenue   482 Total revenue for reportable segments 87,417 113,864 115,556 Operating expense, excluding depreciation and amortization 30,648 49,241 49,229 Operating margin, excluding depreciation and amortization 56,769 64,623 66,327 Additions to long-lived assets 148,622 22,046 30,068 Total assets (end of period) $ 141,280 $ 146,966 $ 138,245 Crude Oil Terminalling Services Service revenue: Third-party revenue $ 16,387 $ 22,177 $ 11,928 Related-party revenue 7,858   Intersegment revenue   704 Lease revenue: Third-party revenue   45 Total revenue for reportable segments 24,245 22,177 12,677 Operating expense, excluding depreciation and amortization 4,197 4,200 3,899 Operating margin, excluding depreciation and amortization 20,048 17,977 8,778 Additions to long-lived assets 2,126 2,194 3,394 Total assets (end of period) $ 71,689 $ 69,149 $ 68,480 Year ended December 31, 2016 2017 2018 Crude Oil Pipeline Services Service revenue: Third-party revenue $ 8,662 $ 9,580 $ 6,396 Related-party revenue 5,433 310 445 Lease revenue: Third-party revenue   484 Product sales revenue: Third-party revenue 20,968 11,094 235,428 Total revenue for reportable segments 35,063 20,984 242,753 Operating expense, excluding depreciation and amortization 15,270 13,310 11,828 Intersegment operating expense 890 417 5,284 Third-party cost of product sales 14,130 8,807 126,776 Related-party cost of product sales   102,469 Intersegment cost of product sales 426 150  Operating margin, excluding depreciation and amortization 4,347 (1,700 ) (3,604 ) Additions to long-lived assets 8,250 2,934 19,654 Total assets (end of period) $ 150,043 $ 117,749 $ 112,429 Crude Oil Trucking Services Service revenue: Third-party revenue $ 25,511 $ 24,529 $ 14,324 Related-party revenue 5,158   Intersegment revenue 890 417 4,580 Lease revenue: Third-party revenue   219 Product sales revenue: Third-party revenue  385 10 Intersegment revenue 426 150  Total revenue for reportable segments 31,985 25,481 19,133 Operating expense, excluding depreciation and amortization 30,156 25,915 19,575 Operating margin, excluding depreciation and amortization 1,829 (434 ) (442 ) Additions to long-lived assets 2,558 1,701 3,243 Total assets (end of period) $ 12,651 $ 7,005 $ 4,150 Total operating margin, excluding depreciation and amortization (1) $ 82,993 $ 80,466 $ 71,059 Total segment revenues 178,710 182,506 390,119 Elimination of intersegment revenues (1,316 ) (567 ) (5,284 ) Consolidated revenues 177,394 181,939 384,835 ____________________ (1) The following table reconciles segment operating margin, excluding depreciation and amortization to income (loss) before income taxes (in thousands): Year ended December 31, 2016 2017 2018 Operating margin (excluding depreciation and amortization) $ 82,993 $ 80,466 $ 71,059 Depreciation and amortization (30,820 ) (31,139 ) (29,359 ) General and administrative expenses (20,029 ) (17,112 ) (15,995 ) Asset impairment expense (25,761 ) (2,400 ) (53,068 ) Gain (loss) on sale of assets 108 (975 ) 149 Equity earnings in unconsolidated affiliate 1,483 61  Gain on sale of unconsolidated affiliate  5,337 2,225 Interest expense (12,554 ) (14,027 ) (16,860 ) Income (loss) before income taxes $ (4,580 ) $ 20,211 $ (41,849 )