Frequencies for tow_veh variable in vehnit dataset :

    VEHICLE |
   TRAILING |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      1,018       91.22       91.22
          1 |         86        7.71       98.92
          2 |          3        0.27       99.19
          5 |          3        0.27       99.46
          6 |          1        0.09       99.55
          9 |          5        0.45      100.00
------------+-----------------------------------
      Total |      1,116      100.00

by Jean Roth , jroth@nber.org , 18 Apr 2016