Previous work has related the Galactic bar to structure in the local stellar velocity distribution .
Here we show that the bar also influences the spatial gradients of the velocity vector via the Oort constants .
By numerical integration of test-particles we simulate measurements of the Oort C value in a gravitational potential including the Galactic bar .
We account for the observed trend that C is increasingly negative for stars with higher velocity dispersion .
By comparing measurements of C with our simulations we improve on previous models of the bar , estimating that the bar pattern speed is \Omega _ { b } / \Omega _ { 0 } = 1.87 \pm 0.04 , where \Omega _ { 0 } is the local circular frequency , and the bar angle lies within 20 ^ { \circ } \leqslant \phi _ { 0 } \leqslant 45 ^ { \circ } .
We find that the Galactic bar affects measurements of the Oort constants A and B less than \sim 2 km~ { } s ^ { -1 } ~ { } kpc ^ { -1 } for the hot stars .