(ShareCast News) - Subscription-based vehicle tracking supplier Quartix Holdings updated the market on its first half trading on Friday, ahead of the publication of its interim results later in the month.Andy Walters, managing director of the AIM-traded firm, said the company continues to make progress in all markets during the period."[We ended] the period with 8,200 fleet customers and 79,000 vehicles under subscription," Walters said."Insurance installations showed strong growth compared to the same period in 2015."We continue to invest in marketing and development initiatives to drive further growth in our core fleet markets, and remain on track to meet profit expectations for 2016," Walters explained.Quartix is due to publish its interim results for the six months to 30 June on 27 July.