A licensing authority must issue a person with a certificate exempting the person from the mobility assistance duties (an "exemption certificate") if satisfied that it is appropriate to do so—
An exemption certificate is valid for such period as is specified in the certificate.
For the purposes of this section "the mobility assistance duties" means—
The driver of a ... taxi is exempt from the mobility assistance duties if—
The driver of a ... private hire vehicle is exempt from the mobility assistance duties if—
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In this section and section 167 "licensing authority", in relation to any area, means the authority responsible for licensing taxis or, as the case may be, private hire vehicles in that area.