Business Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jun. 30, 2012 segment	Jun. 30, 2011
Business Segment Information
Number of reportable segments	3
Business Segment Information
Total revenues	$ 16,304	$ 13,892
Segment income - total income from reportable segments	903	298
Unallocated amounts:
Corporate and other expenses	(1,467)	(1,735)
Amortization of intangible assets	(161)	(100)
Change in fair value of contingent acquisition consideration	334	(17)
Other income, net	5	3
Interest expense, net	(5)	(29)
Income from continuing operations before income taxes	903	272
Total reportable segments
Business Segment Information
Total revenues	16,304	13,892
Segment income - total income from reportable segments	2,197	2,150
Roadway Sensors
Business Segment Information
Total revenues	7,184	6,895
Segment income - total income from reportable segments	1,392	1,540
Transportation Systems
Business Segment Information
Total revenues	8,330	6,997
Segment income - total income from reportable segments	839	610
iPerform
Business Segment Information
Total revenues	790
Segment income - total income from reportable segments	$ (34)