  A Carnot group $\mathbb{G}$ admits Lusin approximation for horizontal curves
if for any absolutely continuous horizontal curve $\gamma$ in $\mathbb{G}$ and
$\varepsilon>0$, there is a $C^1$ horizontal curve $\Gamma$ such that
$\Gamma=\gamma$ and $\Gamma'=\gamma'$ outside a set of measure at most
$\varepsilon$. We verify this property for free Carnot groups of step 2 and
show that it is preserved by images of Lie group homomorphisms preserving the
horizontal layer. Consequently, all step 2 Carnot groups admit Lusin
approximation for horizontal curves.
