Blending two, or more, photos seems the obvious way to do this.
This could be done by applying variable density gradient masks to two images or much more simply by masking or pasting in selected areas of one image into another and then using an edge blending effect of choice.
Note that in this photos and in all the examples on his page there is either a natural dividing line OR an area of demarcation where quite rapid change occurs.
In the example photo that you provided note that there is some well defined intrusion of one scene into the other's 'space' in some locations.
eg whereas down the building edge the boundary is well enough defined, down on the roaD in the middle the car headligt traces cross the centre line without any 'grading' or reduction in brightness. See crop below -
Note: This extract used in accordance with "fair use" policy as recognised by US and international Copyright law. This note added due to deletion of my prior work due to misunderstanding of "fair-use" by person concerned.