The purposes of this study are firstly to measure spatial spillovers of transport infrastructure investment on the influx of population and gross regional domestic products and secondly to present policy implications to enhance the effectiveness of the transportation infrastructure with respect to economic efficiency and balanced regional development. This study utilizes panel data that encompass 226 local autonomies from 2005 to 2016. This study utilizes the 2005 to 2016 panel data to investigate influx of population model and the 2010 to 2016 panel data to analyze the gross regional domestic product model. Through the application of the spatial panel model that best fits the spatial structure of our data, we were able to test our research hypotheses. Based on the findings, this study makes two policy recommendations. First, road accessibility should be improved to target whole regions for equity based on a balanced development strategy instead of concentrating on the nodal region. Second, an increase of railways in the nodal region is closely related to the efficiency gains of neighboring regions. A future policy to target the increase of railway accessibility to a nodal region should go along with an increase in road accessibility of neighboring regions that are connected to the nodal region.