Transportation and traffic theory
Articles in SafetyLit 
 Y-Axis = Volume :: X-Axis = Issue 
?=unknown status :: X=no issue published :: nn=articles from issue :: A=relevant article(s) IDed to add
S=searched, nothing  relevant :: O=issue published but not yet searched :: C=combination issue
|  |  | 
| 6 (1974) | 5 | 
| 8 (1983) | 8 | 
| 9 (1984) | 3 | 
| 12 (1987) | 4 | 
| 12 (1993) | 9 | 
| 13 (1996) | 5 | 
| 14 (1999) | 11 | 
| 15 (2002) | 11 | 
| 16 (2005) | 6 | 
| 17 (2007) | 10 | 
| 18 (2009) | 7 | 
| 19 (2011) | ? | 
| 20 (2013) | ? |