Este vehículo se está incorporando a la circulación, ¿lo hace correctamente?

As a general rule, reversing is prohibited, except in the following cases, exceptionally and always for the shortest distance necessary: 1. As an additional manoeuvre when stopping, parking or joining the traffic. In this case you may not reverse more than 15 metres or enter a road junction. 2. When it is not possible to move forwards, turn or make a U-turn. In this case there is no limit on the reversing distance, and you may even enter a road junction if necessary. Reversing is prohibited on dual carriageways (autovías) and motorways (autopistas). In the case in the question, because it is joining the traffic, it may not travel more than 15 m or enter a junction, so what the blue vehicle is doing is incorrect.