We compensate officers, directors, key employees and consultants with stock-based compensation under the Image Sensing Systems, Inc. 2014 Stock Option and Incentive Plan (the "2014 Plan"), which was approved by our shareholders and is administered under the supervision of our Board of Directors. The 2014 Plan and awards granted under the 2014 Plan were assumed by Autoscope in the Reorganization. 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 three to five years from the dates of the grant, beginning one year from the date of grant, and have a contractual term of nine 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, 2022 and 2021 was $206,000 and $53,000, respectively. At March 31, 2022, 119,873 shares were available for grant under the 2014 Plan.

A summary of the stock option activity for the first three months of 2022 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, 2021		12,000		$	4.90		1.13	$	19,860
Granted		120,000		$	6.87		—	$	—
Exercised		(7,000	)	$	4.55		—	$	—
Expired		—		$	—		—	$	—
Forfeited		(2,000	)	$	7.10		—	$	—

Options outstanding at March 31, 2022		123,000		$	6.81		9.65	$	6,480
Options exercisable at March 31, 2022		63,000		$	6.74		9.47	$	6,480

Stock options to purchase 7,000 shares were exercised, no stock options expired, and options to purchase 2,000 shares were forfeited during the three-month period ended March 31, 2022, and options to purchase 1,000 shares were forfeited during the three-month period ended March 31, 2021. During each of the three-month periods ended March 31, 2022 and 2021, we recognized $146,000 and no stock-based compensation expense related to stock options, respectively. As of March 31, 2022, there was $177,000 of unrecognized compensation cost related to non-vested stock options.

The fair value of stock options granted under stock-based compensation programs has been estimated as of the date of each grant using the multiple option form of the Black-Scholes valuation model, based on the grant price and assumptions regarding the expected life, stock price volatility, dividends, and risk-free interest rates. Each vesting period of an option is valued separately, with this value being recognized over the vesting period. The weighted average per share grant date fair value of options to purchase 120,000 shares granted for the quarter ended March 31, 2022 was $2.32. The weighted average assumptions used to determine the fair value of stock options granted during 2022 is as follows:

The expected life represents the period that the stock option awards are expected to be outstanding and was determined based on historical and anticipated future exercise and expiration patterns. The risk-free interest rate used is based on the yield of constant maturity U.S. Treasury bonds on the grant date with a remaining term equal to the expected life of the grant. We estimate stock volatility based on a historical daily price observation. The dividend yield assumption is based on the annualized current dividend divided by the share price on the grant date.

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. 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.

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.

The following table summarizes restricted stock award activity for the first three months of 2022:

	Number of Shares			Weighted Average Grant Date Fair Value
Awards outstanding December 31, 2021	18,597		$	5.72
Granted	6,996			6.43
Vested	(14,522	)		5.71
Forfeited	—			—
Awards outstanding at March 31, 2022	11,071		$	6.17

As of March 31, 2022, the total stock-based compensation expense related to non-vested awards not yet recognized was $44,000, which is expected to be recognized over a weighted average period of 2.03 years. During the three-month periods ended March 31, 2022 and March 31, 2021, we recognized $60,000 and $53,000, respectively, of stock-based compensation expense related to restricted stock awards.