RoadUpgrade.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class RoadUpgrade : Upgrade
{

    // Start is called before the first frame update
    void Start()
    {
        maxLevelModifier = 2;
    }

    // Update is called once per frame
    void Update()
    {
        
    }

    public void UpgradeRoad()
    {
        UpgradeTargets target = UpgradeTargets.speed;
        Road road = gameObject.GetComponent<Road>();
        City city = gameObject.GetComponent<City>();
        float currentLevel = road.GetLevel(target);
        city.UseResources(GetPrices(currentLevel));
        road.IncreaseSpeed(1 / currentLevel);
        Debug.Log("Road upgraded");
    }

}