X0303 4 2010-04-23 0 0000943034 IMAGE SENSING SYSTEMS INC ISNS 0001044321 MARXE AUSTIN W & GREENHOUSE DAVID M C/O SPECIAL SITUATIONS FUNDS 527 MADISON AVENUE, SUITE 2600 NEW YORK NY 10022 0 0 1 0 Common Stock 2010-04-23 4 P 0 2300 13.41 A 1073720 I By Limited Partnerships Common Stock 2010-04-26 4 P 0 6500 13.413 A 1080220 I By Limited Partnerships This is a joint filing by Austin W. Marxe (Marxe) and David M. Greenhouse (Greenhouse). They share voting and investment control over all securities owned by Special Situations Fund III QP, L.P. (QP), Special Situations Cayman Fund, L.P. (Cayman), Special Situations Technology Fund, L.P. (Tech) and Special Situations Technology II, L.P. (Tech II), respectively. 519,581 shares of Common Stock are held by QP, 149,582 shares of Common Stock are held by Cayman, 73,516 shares of Common Stock are held by Tech and 337,541 shares of Common Stock are held by Tech II. The interest of Marxe and Greenhouse in the shares of Common Stock owned by QP, Cayman, Tech, and Tech II is limited to the extent of his pecuniary interest. This is a weighted average price. Austin W. Marxe 2010-04-27 David M. Greenhouse 2010-04-27