We compensate officers, directors, key employees and consultants with stock-based compensation under the Image Sensing Systems, Inc. 2005 Stock Incentive Plan (the "2005 Plan") and the Image Sensing Systems, Inc. 2014 Stock Option and Incentive Plan (the "2014 Plan"), both of which were approved by our shareholders and are administered under the supervision of our Board of Directors. Although stock options granted under the 2005 Plan are still outstanding, the 2005 Plan expired, and the Company can no longer grant options or other awards under the 2005 Plan. Stock option awards are granted at exercise prices equal to the closing price of our stock on the day before the date of grant. Generally, options vest ratably over periods of 3 to 5 years from the dates of the grant, beginning one year from the date of grant, and have a contractual term of 9 to 10 years.

Compensation expense, net of estimated forfeitures, is recognized ratably over the vesting period. Stock-based compensation expense included in general and administrative expense for the three-month periods ended March 31, 2019 and 2018 was $50,000 and $85,000, respectively. At March 31, 2019, 108,420 shares were available for grant under the Company's 2014 Plan.

A summary of the option activity for the first three months of 2019 is as follows:

	Number of Shares			Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
Options outstanding at December 31, 2018		39,000		$	6.26		2.80	$	4,480
Granted		—		$	—		—	$	—
Exercised		(1,000	)	$	4.22		—	$	950
Expired		—		$	—		—	$	—
Forfeited		(4,000	)	$	4.22		—	$	3,360

Options outstanding at March 31, 2019		34,000		$	6.56		2.20	$	9,420
Options exercisable at March 31, 2019		34,000		$	6.56		2.20	$	9,420

There were options to purchase 1,000 shares of common stock exercised during the three-month period ended March 31, 2019 and no options exercised in the three-month period ended March 31, 2018. During the three-month period ended March 31, 2019 we recognized no stock-based compensation expense related to stock options compared to $1,000 recognized during the three-month period ended March 31, 2018. As of March 31, 2019, there was no unrecognized compensation cost related to non-vested stock options.

Restricted stock awards are granted under the 2014 Plan at the discretion of the Compensation Committee of our Board of Directors. We issue restricted stock awards to executive officers and key consultants. These awards may contain certain performance conditions or time-based vesting criteria. The restricted stock awards granted to executive officers vest if the various performance or time-based metrics are met. Stock-based compensation is recognized for the number of awards expected to vest at the end of the period and is expensed beginning on the grant date through the end of the vesting period. At the time of vesting of the restricted stock awards, the recipients of common stock may request to receive a net of the number of shares required for employee withholding taxes, which can be withheld up to the relevant jurisdiction's maximum statutory rate.

We also issue stock awards as a portion of the annual retainer for each director on a quarterly basis. The stock awards are fully vested at the time of issuance. Compensation expense related to any stock awards issued to employees is determined on the grant date based on the publicly-quoted fair market value of our common stock and is charged to earnings on the grant date.

The following table summarizes restricted stock award activity for the first three months of 2019:

	Number of Shares			Weighted Average Grant Date Fair Value
Awards outstanding December 31, 2018	58,877		$	3.22
Granted	28,644			5.04
Vested	(22,976	)		3.54
Forfeited	(11,826	)		3.04
Awards outstanding at March 31, 2019	52,719		$	4.11

As of March 31, 2019, the total stock-based compensation expense related to non-vested awards not yet recognized was $198,000, which is expected to be recognized over a weighted average period of 2.5 years. During the three-month periods ended March 31, 2019 and March 31, 2018, we recognized $50,000 and $84,000, respectively, of stock-based compensation expense related to restricted stock awards.