Automobiles, introduced into Mount Auburn in 1908, prompted a series of roadway improvements.  A steam roller and crusher were purchased the same year and the old roads were gradually replaced with a new tar macadam surface, which was far more stable than the earlier roads (crushed gravel) and better suited to automobile tires.  Automobile gates were added on either side of the Egyptian gate in 1913; roads were realigned to accommodate greater speeds; and a major repaving project was undertaken to create surfaces appropriate for automobile tires.  Central Avenue was one of the first to be done (image above, 1920).  By 1928, two-thirds of the roads had been rebuilt.

(Master Plan, Vol. 2, pg. 40)