\begin{Schunk}
\begin{Sinput}
 tti_dat <- read.csv(unzip(file.path(ddir, "TTI_Data.csv.zip")), header = TRUE)
 colnames(tti_dat, 20)
\end{Sinput}
\begin{Soutput}
 [1] "Urban.Area"                                    
 [2] "PopGroup"                                      
 [3] "Year"                                          
 [4] "Population"                                    
 [5] "PopRank"                                       
 [6] "Peak.Travelers"                                
 [7] "Commuters"                                     
 [8] "Freeway.Daily.VMT"                             
 [9] "Freeway.Lane.miles"                            
[10] "Arterial.Daily.VMT"                            
[11] "Arternial.Lane.miles"                          
[12] "Transit.Passenger.Miles"                       
[13] "Transit.Passenger.Trips"                       
[14] "Value.of.Time"                                 
[15] "Commercial.Value.of.Time"                      
[16] "Avg..State.Gas.Cost"                           
[17] "Avg..State.Diesel.Cost"                        
[18] "X..Peak.VMT.Congested"                         
[19] "X..Lane.miles.Congested"                       
[20] "Number.of.Rush.Hours"                          
[21] "Gallons.Excess.Fuel"                           
[22] "Gallons.Excess.Ranged"                         
[23] "Gallons.Excess.per.Commuter"                   
[24] "Gallons.per.Rank"                              
[25] "Total.Hours.of.Delay"                          
[26] "Total.Delay.Rank"                              
[27] "Delay.per.Commuter"                            
[28] "Rank"                                          
[29] "Travel.Time.Index"                             
[30] "TTI.Rank"                                      
[31] "Commuter.Stress.Index"                         
[32] "CSI.Rank"                                      
[33] "Freeway.Planning.Time.Index.95"                
[34] "Freeway.Planning.Time.Index.95.Rank"           
[35] "Freeway.Planning.Time.Index.80"                
[36] "Freeway.Planning.Time.Index.80.Rank"           
[37] "Excess.CO2.lbs"                                
[38] "Excess.CO2.Rank"                               
[39] "Excess.CO2.per.Peak.Commuter"                  
[40] "Excess.CO2.per.Peak.Commuter.Rank"             
[41] "Truck.Congestion.Cost"                         
[42] "Truck.Commodity.Value"                         
[43] "Annual.Congestion.Cost"                        
[44] "Annual.Congestion.Cost.Rank"                   
[45] "Congestion.Cost.per.Commuter"                  
[46] "Congestion.Cost.per.Commuter.Rank"             
[47] "Delay.Reduced.due.to.Operations.Treatments"    
[48] "Delay.Reduced.due.to.Operations.per.Commuter"  
[49] "Wasted.Fuel.Saved.by.Operations.Treatments"    
[50] "Congestion.Cost.Saved.by.Operations.Treatments"
[51] "Delay.Reduced.due.to.Transit"                  
[52] "Delay.Reduced.due.to.Transit.per.Commuter"     
[53] "Fuel.Saved.by.Transit"                         
[54] "Congestion.Cost.Saved.by.Transit"              
[55] "Roadway.Congestion.Index"                      
[56] "Presence.of.Urban.Rail.in.2011"                
[57] "Size.Category.of.Urban.Rail.in.2011"           
\end{Soutput}
\end{Schunk}
