As everyone suggested, please do look at the existing research in the area. That said, here are some suggestions I found on what would be the expected best practices in defining dashboard specific content for automobiles.
- Ensure content is visible from a distance : Do note that while you would be hoping that your drivers have good eyesight they will have only a fraction of time to take in information and having content in really small font can make it hard for them to assimilate information. To quote this article about automative UI's
Dashboards are often viewed from a considerable physical distance.
This distance imposes some restrictions on the dashboard's appearance.
Here's a little experiment: open up any text document. After that,
walk away from your desk and get some coffee. When you return, keep
five or six steps distance from the screen and locate the fifth word
of the second paragraph. How long did that take you? And how hard was
it to locate and read the word? From a distance, 12 pt type tends to
blend into the background, becoming barely legible. This means
dashboards can't feature small text, however pretty and aesthetically
pleasing it may be.
Due to the limited space,consider using icons if they are easily recognizable : If you have an icon which is easily recognizable consider just using it rather than providing a lot of text to explain the same reaction. However if the icon is not well known or easily recognized consider supplementing it with text to make it easier to read. I recommend looking at this link to get additional inputs on the type of icons to use.
Define a consistent layout grid : As you rightly pointed out do not try to have too many screens and multiple levels but try to have a well defined and structured grid so that users are accustomed to one layout rather than having multiple layouts to remember. To quote this article:
The grid should account for the majority of the screen to be used to
convey information, with minimal need to scanning. The centered area
is commonly the first accessed by a driver’s vision and therefore is
the best place for immediate feedback.
The standard app structure should account for 3-4 major zones of
activity:
Main Content Area Primary navigation / feature set access Action areas
for current task Alerts and notices (both active and passive) Once the
basic grid has been established, it should not be altered for fringe
cases of activity. During the design process, the grid will adjust as
needed, but final design should have a locked structure.
Note the grid does not have to be mathematically relevant, but
designed for need and size of available screen size, activity and
content.
The active areas of the screen should be considered for easy recall of
action for the driver.
Recall of driver is imperative in any in-dash application. For most purposes, assume the driver has 1-2 items of focus at any time, with
less than 2 seconds of driver attention per action or interval. Any
additional demands of driver’s cognitive space will cause distraction
and unsafe driving.
This restriction will allow for the emergence of
an active UI that minimizes distraction and places focus on the core
even that is occurrin
- Contrast and color : I recommend looking at some of the answers in this question "Dark screens in cars" as that will give some additional inputs on the need for sufficient contrast to ensure information can easily discerned at a glance. Also to quote the above mentioned article
Use of contrast to indicate changes to state or draw users attention
to important items is critical. Use strong solid colors with clear
text rather than shaded, extruded or beveled buttons in conjunction
with text with visual effects.
Keep in mind the screen type may render some colors / color
distinction invisible in direct sunlight, while other screen types may
have glare that will cause difficulty in viewing low contrast color
palettes.
A good rule of thumb is to initially design your application entirely in grayscale and textures. This will allow for an
understanding of contrast and differentiation needed for proper use of
the UI. As you add color to the design, be aware of how the addition
enhances or degrades the usability and visual acuity of the UI.
- Nighttime Viewing: While your design might stand the test of time in day time viewing you need to also consider for the fact that the contrast and brightness levels will be different at night time. To quote this article
When dealing with color and contrast, be aware of the brightness of
the interface during night driving, and the potential of the device to
affect the eyesight of the driver.
In most cases, having a darker or neutral background should be
considered for this reason alone. A stark white background will have
effect on the ability of the driver to conduct safe driving in dark
environments.
Some devices will have the ability to dim, if so, consider how the
dimming affects the UI, whether or not there is a nighttime view, or
if the dimming is a user-controlled part of the interface.
If a separate night view, or any selection of views is considered in
the design, first be aware of any auto-dimming abilities of the
device. Selection of modified views is simply a compounded learning
effort by the driver and not something that should be expected to be a
known attribute.
- Voice and Gestural Commands : I am not sure if you are considering this as part of your design\implementation phase but there are a few considerations to consider here as well as quoted below
Understand that audio have limitations based on the host device’s
integration with the vehicles existing audio input and speaker system.
This will need to be assessed specifically when a software/hardware
and I/O protocol are established.
Gestures are becoming more and more useful and obvious to many
consumers and can lead to activating key areas of the application
without needing the driver to focus on the device visually.
If gestures are to be used, consider basic driving issues such as
unintentional rapid scrolling, or the vehicle itself moving at
inopportune moments.
Also ensure that primary activities are not dependent on gestures alone as the focus on performing the specific gesture can be a distraction to the user as mentioned in this article about the Cadillac gesture based system
If a driver moves his or her right hand within 8 inches of the center
touch-screen of a Cadillac equipped with the CUE infotainment system,
the screen illuminates and displays icons for more features.
But systems such as CUE can be controversial. Consumer Reports blasted
CUE in a blog posting two months ago as potentially causing more
driver distraction. Because the screen doesn't brighten until your
hand gets close to the display screen, it might be harder to zero in
on a particular icon from among many.
I also recommend listening to this excellent talk Trip O'Dell: If UX Can Kill it Probably Will - Designing for the 70 MPH Interface as it gives excellent inputs on how to design for car based interfaces and what you should consider.
I also recommend looking at this excellent article on how Tesla defined the user experience for its Tesla Model S
..please familiarize yourself with the research in this domain, that is what I'm trying to do!! :-)