Year Jan. Feb. Mar. Apr. May. Jun. Jul. Aug. Sep. Oct. Nov. Dec. 24-Hour Annual Avg. 1998 14467 11997 8361 1999 10139 10460 11806 13460 15062 17594 19378 21411 19365 16511 14611 13165 15247 2000 10162 10934 12405 13966 15586 17890 20840 18899 15546 13488 12078 11124 14410 2001 10395 10890 12226 13068 15707 18383 20148 21196 11222 2002 10424 11372 11779 14947 16176 19357 21242 21283 18433 14753 12587 11399 15313 2003 10165 10932 12740 13523 15437 19681 21540 23130 15828 2004 21120 17873 15828 13497 12021 2005 2006 2007 2008 2009 2010 2011 2012 2013 9073 10837 12822 14713 18150 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024