LEASES

We have operating lease commitments for office and terminal properties, revenue equipment, and computer and office equipment, and we have capital lease commitments for revenue equipment, in each case excluding owner/operator rentals and month-to-month equ

ipment rentals, summarized for the following fiscal years (in thousands):

	Operating		Capital
2018	$	73	$	3,606
2019		73		3,606
2020		73		5,813
2021		-		5,368
202 2		-		5,175
Thereafter		-		3,383
Total minimum lease payments	$	219	$	26,951
Less: amount representing interest				(2,212	)
Present value of minimum lease payments				24,739
Less: current portion				(2,962	)
Capital lease obligations, long-term			$	21,777

A portion of our operating leases of tractors and trailers contain residual value guarantees under which we guarantee a certain minimum cash value payment to the leasing company at the expiration of the lease. We estimate that the undiscounted value of th

e residual guarantees is approximately

$4.0

million at

December 31, 2017

and

2016,

respectively. The residual guarantees at

December 31, 2017

expire between

August 2018

and

February 2019.

We expect our residual guarantees to approximate the market value at the end of the lease term. Additionally, certain leases contain cross-default provisions with other financing agreements and additional charges if the unit's mileage exceeds certain thresholds defined in the lease agreement.

Rental expense is summarized

as follows for each of the

three

years ended

December 31:

(in thousands)	2017		2016		2015
Revenue equipment rentals	$	12,055	$	10,773	$	12,611
Building and lot rentals		448		708		2,078
Other equipment rentals		261		254		340
	$	12,764	$	11,735	$	15,029