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We have observed 99 mid-infrared-bright, massive young stellar objects andcompact HII regions drawn from the Red MSX source (RMS) survey in the J=3$-$2transition of $^{12}$CO and $^{13}$CO, using the James Clerk Maxwell Telescope.89 targets are within 6 kpc of the Sun, covering a representative range ofluminosities and core masses. These constitute a relatively unbiased sample ofbipolar molecular outflows associated with massive star formation. Of these,59, 17 and 13 sources (66, 19 and 15 percent) are found to have outflows, showsome evidence of outflow, and have no evidence of outflow, respectively. Thetime-dependent parameters of the high-velocity molecular flows are calculatedusing a spatially variable dynamic timescale. The canonical correlationsbetween the outflow parameters and source luminosity are recovered and shown toscale with those of low-mass sources. For coeval star formation we find thescaling is consistent with all the protostars in an embedded cluster providingthe outflow force, with massive stars up to $\sim$30 M$_{\odot}$ generatingoutflows. Taken at face value, the results support the model of a scaled-upversion of the accretion-related outflow-generation mechanism associated withdiscs and jets in low-mass objects with time-averaged accretion rates of$\sim$10$^{-3}$ M$_{\odot}$ yr$^{-1}$ onto the cores. However, we also suggestan alternative model, in which the molecular outflow dynamics are dominated bythe entrained mass and are unrelated to the details of the accelerationmechanism. We find no evidence that outflows contribute significantly to theturbulent kinetic energy of the surrounding dense cores.

A distance limited sample of massive molecular outflows