  The aim of our study is to use dynamical simulations to explore the influence
of two important dynamical bar parameters, bar strength and bar pattern speed,
on the shape of the bar dust lanes. To quantify the shape of the dust lanes we
have developed a new systematic method to measure the dust lane curvature.
Previous numerical simulations have compared the curvature of bar dust lanes
with the bar strength, predicting a relation between both parameters which has
been supported by observational studies but with a large spread. We take into
account the bar pattern speed to explore, simultaneously, the effect of both
parameters on the dust lane shape. To that end, we separate our galactic bars
in fast bars $\left(1 < \mathcal{R} < 1.4 \right)$ and slow bars
$\left(\mathcal{R} > 1.4 \right)$, obtaining, as previous simulations, an
inverse relation between the dust lane curvature and the bar strength for fast
bars. For the first time, we extend the study to slow bars, finding a constant
curvature as a function of the bar strength. As a result, we conclude that weak
bars with straight dust lanes are candidates for slow bars. Finally, we have
analysed a pilot sample of ten S$^4$G galaxies, obtaining dust lane curvatures
lying within the range covered by the simulations.
