As the Texas Department of Transportation begins exploring the possibility of adding two managed toll lanes in each direction on I-35, some readers may wonder how their toll dollars are used. Tolls pay for more than just building new toll roads. Although tolls do go toward repaying the bonds sold to fund construction of new roads, they also pay for operating and maintaining the existing roadways and funding expansions and improvements. The state’s population is projected to increase to more than 30 million people by 2020, according to the Department of State Health Services. As the population increases, toll roads may undergo improvement projects to accommodate for the increased traffic congestion. Regularly scheduled increases of toll rates also help pay for future projects. Gas taxes and vehicle registration fees do not fund the toll roads. That revenue is used to fund nontolled projects by TxDOT. Toll roads, on the other hand, are largely funded through the sale of bonds, which are repaid through tolls.