§ 181. Liability for damage to property in transit. Every common carrier of property by motor vehicle shall, upon demand, issue either a receipt or a bill of lading for all property delivered to it for transportation. No contract, stipulation or clause in any receipt or bill of lading shall exempt any common carrier of property by motor vehicle from any liability for loss, damage or injury caused by it to property from the time of its delivery for transportation until the same shall have been received at its destination and a reasonable time shall have elapsed after notice to the consignee of such arrival to permit the removal of such property and inspection; provided, however, that when expressly authorized or required by order of the commissioner a carrier may establish and maintain rates dependent upon the value declared in writing by the shipper or agreed upon in writing as the released value of the property, in which case such declaration or agreement shall have no other effect than to limit liability and recovery to an amount not exceeding the value so declared or released and shall not, so far as relates to values, be held to violate this article. Every common carrier of property by motor vehicle shall be liable for all loss, damage or injury to property caused by delay in transit due to negligence while the same is being carried by it, but in any action to recover for damages sustained by delay in transit the burden of proof shall be upon the defendant to show that such delay was not due to negligence. Nothing in this section shall deprive any holder of such receipt or bill of lading of any remedy or right of action which such holder has under existing law.