Developing infrastructures such as roads for private uses of vehicles is more essential than innovating public transport systems. This question has been going on for ages yet has no clear answer. Personally, I disagree with the idea of upgrading the traffic systems for private means of transport. (The adjective "essential" is non-gradable and may not require a qualifier)
On the one hand, using expenses on expanding streets or adding more lanes into roads could be a possible solution to traffic jams but many consequences could also be obviously foreseeable. When a road is under construction, the people normally using the road will have to take another direction which is time-consuming. In addition, building roads or widening streets will cost an arm and a leg. Especially if the infrastructure needs to be reconstructed, it will take even more resources.
On the other hand, innovating a convenient system for mass transportation perhaps could be more efficient as well as cost-saving. Having a modern public mean of transport could encourage the residents of one city to reduce their use of private vehicles which is a direct cause of congestions. Moreover, a well-designed system could bring an innovative appearance to the city or a country. There have been many newly-designed concepts of public transportation shown on the internet recently. Thanks to the rapidly developing technology, the future of a world without traffic problems is are near.
To put in a nutshell, developing public transportation is the most realistic solution to traffic problems which have been a hot potato in many countries. Since the traffic system of a country could directly impact its economy and growth, the problem needs to be carefully examined and the authorities need to quickly get down to action.