The Unification Era spans specifically from either 2003 or 2008 through 2011. By the time of the formal 2008 unification, it was contested with the aforementioned "spec car", the &lt;a href="Dallara%23Third%20generation%20%28IR-03%20/%20IR-05%29"&gt;Dallara IR03/05&lt;/a&gt; powered by the normally aspirated Honda V-8 engines. With the sudden influx of former Champ Car teams and drivers, and an abundance of available rolling chassis, fields briefly grew. For a few years, bumping returned to time trials, and the era was highlighted by the 100th Anniversary of the Indianapolis 500 in 2011.