The biggest thing to consider more than what hardware needs to be installed on your forklift is what do you want the vehicle management system for? OSHA checklist, access control, 2-way paging, motion and lift monitoring, speed, lift weight, impact, location, etc. How painful are these issues to you...

Some things to keep in mind when evaluating the vehicle management system:

1) WMS typically does not have a vehicle interface for access control or vehicle monitoring (lift time, speed, motion time, etc.) - therefore, at a minimum, hardware is required on the vehicle, it may just not require dashboard space.
2) WMS usually does not have an access ID input such as a prox card reader. So one would typically need to be added to the dashboard. They also want it on, when the WMS may not be because WMS drains power, it is usually shut off when vehicle is not used. If prox is on and WMS off, that poses other issues. Such as, if someone tries to log into the forklift to drive and doesn't want to log into the WMS, do they have a display to indicate whether they are authorized and provide feedback to the operator re: why access was granted or not.
a. Very often, not every forklift or tug operator has a WMS login and would not be eager to login to a WMS simply to drive/move a vehicle. Very convenient to simply swipe a badge and start a truck vs. a 1-2 minute login process (with failure potential, password to reset, etc.).
3) if a page comes in, where would the indicator light be? If an impact or even triggered checklist occurs, what prompts the operator to switch applications or even alert the operator of a needed checklist? Will the operator really switch between applications? what would force/prompt that, espeically if they are in the middle of a ERP application?
4) features like the impact sensor and location typically would be desired when the vehicle's WMS is off...
a. for example, finding a vehicle that is not being used (and is available for use)
b. when an impact occurs (if operator is not logged in), recreating the situation - angle of accident, not moving, magnitude, etc.

Lastly, can your VMS data be integrated with the WMS data to provide the highest level of visiblity?

Dan:
We have been evaluating all the major brands. Recently we have moved to the next step and installed a few Shockwatch Fleet Control Units to assess their performance. The reason we chose them is because they integrate with our onboard lift truck inventory control devices. No need for additional (driver obstructive) control units mounted on the trucks, no additional attennas or recievers etc. So far results look promising. Best of all the vehicle operators have become much safer almost over night!!!!
To conduct a true evaluation you need to know the costs associated with damaged caused by your fleet. Then after implementation the reduced costs will pay for such systems.