The cost of constructing a rich digital twin of a road currently outweighs its benefits. This is the prevailing industry view even though a simple highway geometric digital twin has the potential to boost cost, time, quality, safety and sustainability performance. This paper presents a review of the current state of the art in practice and research in constructing and maintaining highway digital twins, focusing on road infrastructure geometry and relationships. The authors calculate frequent highway assets for prioritisation and construct geometric digital twins in commercial software to estimate costs. The authors also highlight the limitations, identify gaps in knowledge and propose research directions.