As Austin continues to expand, the congestion and traffic will keep breaking records of all-time highs. Employing stopgap solutions like widening highways will only be temporary reliefs but will inevitably leave Austin in the same position it is now (minus the budget and years of work) as density on the roads swells to match the new size. The traffic is a systemic problem based on the distance between residential centers and places of employment, and without changing the current system the problem will remain.
My proposition, despite the naysaying of the Simpsons, is the implementation of a monorail which would run parallel to Austin's largest highways reaching out to residential areas. A train like the Disney World monorail system or the Tokyo Monorail airport link which respectively shuttle 150,000 and 300,000 passengers daily set up as a direct line into Austin's city center would not only be a more direct means of commute but in ferrying those passengers it would free up an equal amount of space on the roads for those still driving, greatly reducing congestion both on highways and within the city streets. With a reduction in internal congestion the city's existing public transport infrastructure in the form of buses would be able to move more freely and residents could use those to navigate within Austin proper, assuming that their place of work is more than a brisk walk from the monorail station. Alternatively a dedicated shuttle bus system could be devoted to the monorail, but that seems unnecessary when the existing bus system can be made functional.
I believe that this project, while daunting, is not only functional and feasible to construct but economically viable in the long-term. If nothing else, knowing that Disney makes use of a well-used monorail to enable visitors to navigate Disney World suggests that it is the effective decision as I cannot imagine Disney doing anything economically unsound, nor can I imagine Tokyo's airport system which was designed with a high population density in mind to be inefficient in its operation.