Supplementary Financial Information (Details 3) (USD $)	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Nov. 30, 2011 BTS	Mar. 31, 2014 Roadway Sensors	Mar. 31, 2013 Roadway Sensors	Mar. 31, 2012 Roadway Sensors	Mar. 31, 2014 Transportation Systems	Mar. 31, 2013 Transportation Systems	Mar. 31, 2012 Transportation Systems	Mar. 31, 2014 iPerform	Mar. 31, 2013 iPerform	Mar. 31, 2013 iPerform BTS	Jun. 30, 2013 iPerform MET
Activity related to carrying value of goodwill
Balance at the end of the year	$ 25,288,000	$ 25,288,000	$ 25,288,000		$ 8,214,000	$ 8,214,000	$ 8,214,000	$ 14,906,000	$ 16,278,000	$ 17,074,000	$ 2,168,000	$ 796,000
Accumulated impairment losses	(7,970,000)	(7,970,000)	(7,970,000)					(7,970,000)	(7,970,000)	(7,970,000)
Goodwill, net	17,318,000	17,318,000	17,318,000	796,000	8,214,000	8,214,000	8,214,000	6,936,000	8,308,000	9,104,000	2,168,000	796,000	796,000	1,372,000
Activity related to warranty reserve
Balance at beginning of fiscal year	169,000	231,000	279,000
Additions charged to cost of sales	179,000	139,000	86,000
Warranty claims	(164,000)	(201,000)	(134,000)
Balance at end of fiscal year	$ 184,000	$ 169,000	$ 231,000