traffic_cop: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/traffic_cop - from package: trafficserver

You may install the required package with command yum install {package}
Error in other languages:
traffic_cop: bevel nie gevind nie
traffic_cop: comandă negăsită
traffic_cop: comando não encontrado
traffic_cop: commande introuvable
traffic_cop: command not found
traffic_cop: käsku ei ole
traffic_cop: không tìm thấy lệnh
traffic_cop: komanda nerasta
traffic_cop: Kommando nicht gefunden.
traffic_cop: kommandot finns inte
traffic_cop: komut yok
traffic_cop: nie znaleziono polecenia
traffic_cop: níor aimsíodh an t-ordú
traffic_cop: no se encontró la orden
traffic_cop: no s'ha trobat l'ordre
traffic_cop: opdracht niet gevonden
traffic_cop: parancs nem található
traffic_cop: perintah tidak ditemukan
traffic_cop: príkaz nenájdený
traffic_cop: příkaz nenalezen
traffic_cop: команда не найдена
traffic_cop: командата не е открита
traffic_cop: 命令找不到
traffic_cop: コマンドが見つかりません