I wrote about automobile streamlining in both the technical and stylistic senses here and here. Now I'd like to mention a body style introduced by Renault at the October 1934 Paris auto show that was a first tangible step in the streamlining direction, a step roughly in line with what a few American manufacturers were doing at the time. (I exclude the larger step made by Chrysler with its Airflow that was introduced for the 1934 model year.)
I said "tangible step" because effort was made to go beyond essentially cosmetic streamlining features such as fender skirts and slightly inclined radiator grilles such as appeared a year or two earlier; I'll explain in the photo captions below.
One side-detail I find interesting is the fact that Renault was able to afford to put these changes into production, given their total output in those days -- about 55-60,000 cars per year. And that production was divided amongst three different body/chassis types: the low-end "Quatre," the mid-high range "Stella," "Nerva" and "Viva" lines (variations on the same package) and the semi-streamlined "Grand Sport" shown below. I don't have enough data at hand, so my guess is that French cars, small and large, were relatively more expensive than American equivalents. Otherwise, how could Renault and other firms remain in business and keep up with the technological and styling theme times?
Let's look at the Renault Grand Sports that were designed in 1933 or thereabouts.
Gallery
Here's a 1935 Nerva Grand Sport at one of the concours popular in France at the time. Note the sloped, V'd windshield, the sloped grille and the blending of the headlights into the fenders. These features surely improved aerodynamic efficiency somewhat. The sides of the car had partial streamlining despite what the swoopy fender line might suggest.
Another concours, this featuring a convertible version of the Grand Sport (note the English spelling of "Grand").
This side view shows that even though traditional fender profiling was preserved, fenders and running boards were in low relief compared to nealy all contemporary automobiles.
The view from above is useful because it shows that the front, hood and top were indeed noticeably more aerodynamically efficient than previous designs featuring vertical fronts, detached headlights and so forth.
This is a fragment of a publication I include to show what the rear windows looked like. Click to enlarge.
Compare the Renault to this 1935 Hupmobile. The Hupp also features embedded headlights and a sloping grille and windshield. However, the latter is a three-pane "wraparound" style rather than a two-pane vee. The sides of the Hupp are high-relief, typical styling practice until near the end of the decade.
This is Studebaker's Land Cruiser for 1934. Its curved rear and multi-pane back window design is in advance of nearly all 1934 competition and in the same spirit as the Renault. The rest of the car is conventional.