Business Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jun. 30, 2013 item	Jun. 30, 2012
Business Segment Information
Number of reportable segments	3
Business Segments
Total Revenues	$ 17,030	$ 16,304
Segment operating income (loss)	669	903
Unallocated amounts:
Amortization of intangible assets	(161)	(161)
Change in fair value of contingent consideration	(7)	334
Other (expense) income, net	(3)	5
Interest expense, net	(4)	(5)
Income from continuing operations before income taxes	662	903
Total reportable segments
Business Segments
Total Revenues	17,030	16,304
Segment operating income (loss)	2,254	2,197
Unallocated amounts:
Corporate and other expenses	(1,417)	(1,467)
Amortization of intangible assets	(161)	(161)
Change in fair value of contingent consideration	(7)	334
Other (expense) income, net	(3)	5
Interest expense, net	(4)	(5)
Income from continuing operations before income taxes	662	903
Roadway Sensors
Business Segments
Total Revenues	7,529	7,184
Segment operating income (loss)	1,214	1,392
Transportation Systems
Business Segments
Total Revenues	8,258	7,849
Segment operating income (loss)	1,286	856
Transportation Systems | Advanced traveler information systems
Unallocated amounts:
Number of advanced traveler information systems	511
iPerform
Business Segments
Total Revenues	1,243	1,271
Segment operating income (loss)	$ (246)	$ (51)