We analyze the impact of transportation infrastructure capital and its maintenance status on regional economic production, exploiting panel data on the German county level (N=401) from 2007 through 2016 in a spatial translog production function. Various SLX and SDEM models are estimated using FGLS and GMM estimators accounting for endogeneity. We find a positive impact of the transport infrastructure capital locally and supra-regionally, and pro-vide evidence that insufficient maintenance and low infrastructure conditions significantly slow economic growth. The analysis shows that this effect is mainly driven by the Bun-desstraßen network as the backbone of the regional German road system.