In order to increase traffic safety in the Netherlands, the government implemented the GOW30-policy. However, evaluation of this policy shows that drivers do not comply with this newly imposed speed limit sufficiently. For this reason, roads need to be designed in such a way that speed limits are perceived as credible. At the same time, the need for sustainable road designs arises, due to factors as increased urban heat stress and population growth. Thus, road designers need to make trade-offs between spatial quality and mobility. Incorporating greenery is a promising way to reduce urban heat stress, but the presence of greenery, particularly thick trees, can also increase the severity of traffic accidents. This study evaluated the impact of roadside greenery on driving behaviour, utilising a driving simulator experiment complemented by a post-experiment survey. Linear Mixed Model analyses (LLM’s) together with survey insights revealed that perceived driving comfort leads to increased driving speeds. Comfort increases on wider roads and on roads with more overview. For this reason, it is not recommended to incorporate low greenery on GOW30 roads. Moreover, high and dense greenery is shown to reduce driving speeds while promoting better positioning on the road. It is furthermore recommended that research is performed in real-life, whilst evaluating roadside greenery in combination with cycling lanes under varying traffic and weather conditions.