Since this is an opinion question you can take it either way.
Pros:
- lower speed may cause lower speed accidents, which are less deadly than their high speed alternatives
- lower speed could potentially allow people to get lost less often because they are able to navigate and respond earlier
- gas savings from optimal operating conditions (between 88.5 - 96.5 km/h [55-60 mph])
Cons:
- longer commute times
- less enjoyable (if you enjoy driving fast)
- may contribute to overall congestion and increase in accidents as people spend more time on average on the roads
Either way, support our opinion and you'll be right.