Vehicles can be run with no emissions of CO2. The main technique is electric cars which can be powered by accumulators or hydrogen fuel cells. Accumulators give a shorter driving range, generally takes a long time to reload and uses much materiel while hydrogen powered cars (HPC) can have a supply for longer distances and reload in a couples of minutes. In this perspective hydrogen is one path to follow. Thus this path must be explored in the short run, in a somewhat longer perspective and for a longer period.
Car companies have published plans to start the marketing of HPC during 2015. In the short run there is a moment 22: There are almost no hydrogen taps for cars thus the market for HPC is very limited and as there are almost no HPCs there is no market for hydrogen taps. Such taps have to be available all over the US to support HPC market.
There are examples of local hydrogen taps in use producing hydrogen by electrolysis. This excludes the transportation of hydrogen to the taps. The trick to spread the establishing of such taps is to use the simultaneously electrolytically produced oxygen. Thus combined stations for hydrogen taps and oxygen can be built at sites where there is a demand for oxygen. There are several such sites.
One example where oxygen is needed are large hospitals. They use oxygen which is transported and stored in liquid form. Large hospitals are spread all over US. If the hydrogen production at a hospital is higher then the demand from vehicles there are at least two options. To use HPC for their own transpositions and even more important to use hydrogen for large fuel cells to substitute their fossil powered reserve aggregates for electric power when the grid fails. This production could also be used to even the top loads at the grid, producing hydrogen at low loads and using the fuel cell electricity at high loads. This will lower the electricity bills and can be of general use in society at the same time as hydrogen taps are provided.
Another example is the environmental efforts to restore lakes with dead bottoms due shortage of oxygen caused by eutrophication or other causes. It has been demonstrated that oxygen restores such bottoms. A combined electrolysis hydrogen tap and oxygen production plant at a road near a not too deep lake can lead the oxygen and release it at the dead bottom. Such a practice would help to establish hydrogen taps. It is up to your imagination to find other sites in demand for oxygen to do the same trick.
In a second perspective, when the demand for hydrogen in the traffic is larger then what is produced locally as described, the next step is to use the current industrially produced hydrogen. There are large quantities of hydrogen produced, for instance in production of chlorine. That hydrogen is used mainly for local energy consumption like producing steam. There has been no incentives for these industries to compress, store and distribute hydrogen for use in vehicles as there has been no market for it. It is much more climate smart and even more profitable to sell and distribute this hydrogen for transportation means.
In the long run there are huge quantities of fossil resources in the ground that are nonburnable if the goals of limiting the CO2 content in the air should be achieved. In this situation there will develop a race to convert oil and coal to hydrogen and to put the waste CO2 back into the earth in a stable manner. The owners of fossil resources who can manage this will still have possibilities to make a profit of their resources by providing hydrogen in large quantities. The others will have a ban on the extraction of their fossil assets. As electricity in the grid and hydrogen has the possibilities to become the major energy carriers in society there will also be incentives for private and corporate actors to use water, wind and sunlight as sources for both these purposes.