# Road Infrastructure Challenges Faced by Automated Driving: A Review
## 4 Identification of Challenges
### Harmonisation  
Studies that investigated improvements of the traffic signs and road markings through a literature review, stakeholder interviews and tests have highlighted harmonisation as one of the main challenges for a smooth transition towards a higher level of automation [10, 11, 19]. Despite standards for traffic signs, such as the US Manual of Uniform Traffic Control Devices (MUTCD) and the Vienna Convention, many countries and jurisdictions apply their own rules and implementations. Nonharmonised signs and markings result in higher efforts required in data collection and training of recognition algorithms, which is also of increased interest for digitalisation. Besides data collection, digitalisation also requires the harmonisation of formats and protocols for data transfer.  
When discussing harmonisation, many questions that require addressing can be identified:  
* Who should be involved in the harmonisation of road infrastructure?
* Who benefits the most and what are the benefits of harmonisation?
* How long should the adaptation period be?
* To what extent should harmonisation be realised?  
Harmonisation extends to the international level and, therefore, it is important that is managed by international legislation bodies and organisations. However, road authorities and vehicle manufacturers are the ones that need to define requirements and technical content. Vehicle manufacturers together with their suppliers and research institutes are aware of the technical capabilities and limitations of ADAS; it is their responsibility to provide requirements to increase the reliability of ADAS. Nevertheless, road authorities have permission to change the road infrastructure. Therefore, to successfully adapt harmonisation, cooperation between those two stakeholders should be well established. Harmonisation would remove the big burden on data collection and training recognition algorithms. That is the reason why vehicular manufacturers may benefit the most from it, though this would, to some extent, also be of benefit to the human driver in the long term. Reaching a consensus and changing signs and markings takes time and comes at some cost, especially for road authorities, which may result in resentment. However, clear guidance and extensive cost-benefit analysis could soften the process. Moreover, in the long-term, additional costs could, to some extent, be compensated through the simplification of future digitalisation processes and the exchange of common expertise and processes, which could be one of the areas of increased demand in the foreseeable future, as digitalisation will open new jobs and opportunities. We can observe that in all these actions--reaching consensus or compliance of human drivers, asking for time and, thus, the harmonisation--should be looked at as a long-term process that could take place in parallel with the transition towards self-driving. To avoid unnecessary costs, the replacement can be done during maintenance. How broad this harmonisation should go is a question of geography, culture and the daily implications of the transition for people, so it would make sense to include at least the largest landmasses under common regulation. Yet, several studies raised concern about the comprehensiveness of traffic signs from a tourist perspective, which would lead to extending the harmonisation even further [74, 75]. Although the parameters of road infrastructure such as shape, colours, fonts for traffic signs or colour and width for road markings are well recognised among all people, the text that often accompanies them is more a matter of culture and language and, therefore, is more difficult to harmonise. However, through digitalisation and the appearance of smart signs and markings, translation of the text to a machine-readable format is achievable.