Complex sentence: At the start of the concessions service quality greatly improved, and traffic began to grow again, and more locomotives and rolling stock were needed and the private companies became increasingly reluctant to make the investment required to increase capacity and service quality began to decline again.
Split into simpler sentences: At the start of the concessions service quality greatly improved, and traffic began to grow again. However, as more locomotives and rolling stock were needed the private companies became increasingly reluctant to make the investment required to increase capacity and service quality began to decline again.