"Modular Vehicle Settings": {
    "MediumCar": {
      "Purchasable": true,
      "Display Name": "Medium Modular Car",
      "Use Permission": true,
      "Permission": "vehiclelicence.mediumodularcar",
      "Distance To Spawn": 5.0,
      "Time Before Vehicle Wipe (Seconds)": 0.0,
      "Maximum Health": 0.0,
      "Can Recall Maximum Distance": 0.0,
      "Can Kill Maximum Distance": 0.0,
      "Minimum distance from player to recall or spawn": 3.0,
      "Remove License Once Crashed": false,
      "Purchase Prices": {
        "scrap": {
          "amount": 2400,
          "displayName": "Scrap"
        }
      },
      "Spawn Prices": {
        "metal.refined": {
          "amount": 50,
          "displayName": "High Quality Metal"
        }
      },
      "Recall Prices": {
        "scrap": {
          "amount": 8,
          "displayName": "Scrap"
        }
      },
      "Commands": [
        "medium",
        "mediumcar"
      ],
      "Spawn Cooldown (Seconds)": 9000.0,
      "Recall Cooldown (Seconds)": 30.0,
      "Cooldown Permissions": {
        "vehiclelicence.vip": {
          "spawnCooldown": 4500.0,
          "recallCooldown": 10.0
        }
      },
      "Amount Of Fuel To Spawn": 0,
      "Refund Fuel On Kill": true,
      "Refund Fuel On Crash": true,
      "Refund Inventory On Kill": true,
      "Refund Inventory On Crash": true,
      "Refund Engine Items On Kill": true,
      "Refund Engine Items On Crash": true,
      "Refund Module Items On Kill": true,
      "Refund Module Items On Crash": true,
      "Drop Inventory Items When Vehicle Recall": false,
      "Chassis Type (Small, Medium, Large)": "Medium",
      "Vehicle Module Items": [
        {
          "shortName": "vehicle.1mod.cockpit.with.engine",
          "healthPercentage": 50.0
        },
        {
          "shortName": "vehicle.1mod.rear.seats",
          "healthPercentage": 50.0
        },
        {
          "shortName": "vehicle.1mod.flatbed",
          "healthPercentage": 50.0
        }
      ],
      "Vehicle Engine Items": [
        {
          "shortName": "carburetor2",
          "conditionPercentage": 20.0
        },
        {
          "shortName": "crankshaft2",
          "conditionPercentage": 20.0
        },
        {
          "shortName": "piston2",
          "conditionPercentage": 20.0
        },
        {
          "shortName": "sparkplug2",
          "conditionPercentage": 20.0
        },
        {
          "shortName": "valve2",
          "conditionPercentage": 20.0
        }
      ]
    }
  },​

I tried added that but get this in the console when i reload the plugin.

Failed to initialize plugin 'VehicleLicence v1.7.9' (NullReferenceException: Object reference not set to an instance of an object) at Oxide.Plugins.VehicleLicence.Init () [0x00174] in <908e302ebeb44749b4dad5a8f59d1cd7>:0 at Oxide.Plugins.VehicleLicence.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00051] in <908e302ebeb44749b4dad5a8f59d1cd7>:0 at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <80b90e8213db44b29ec2d4111764172c>:0 at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in :0 at Oxide.Core.Plugins.CSPlugin.HandleAddedToManager (Oxide.Core.Plugins.PluginManager manager) [0x00043] in :0

I did validate the file and it was valid. So no idea why its not working