The same parking space cannot contribute to both SSc4.3 and SSc4.4 by being designated for low-emitting and fuel-efficient vehicles (SSc4.3) and carpools or vanpools (SSc4.4).   

A residential building in a dense urban area that does not have parking facilities may favor a vehicle-sharing program as a way of attracting new tenants and earning the credit at the same time. 

If the project team is committed to creating a comprehensive transportation management plan to qualify for an Exemplary Performance point through IDc1, dedicating the resources upfront to develop and implement a vehicle-sharing program makes sense, as it will be folded into the broader transportation plan.

Consider the preference of building occupants so as not to dedicate resources to programs or infrastructure that will remain idle and not serve their intended audience. Is the organizational culture such that employees would appreciate such amenities? Depending on the building type, building occupants can be surveyed to assess the demand for amenities relating to low-emitting and fuel-efficient vehicles. If you are planning on providing alternative-fuel refueling stations, assess what kind of fuel is preferred.

Consider the feasibility of each option based on your site location. Is your project located in a dense urban environment where most people commute to work via mass transit, or are you in a suburban or rural area where most people drive to work, and may appreciate a vehicle-sharing program? Also consider things like whether there are alternative-fuel vehicles used by occupants or whether occupants tend to use low-emitting and fuel-efficient vehicles. Are HOV (high-occupancy vehicle) lanes available? These types of questions will help to determine an appropriate approach to this credit.

Simply providing preferred parking for low-emitting and fuel-efficient vehicles is the easiest way to comply with this credit. It is also a low-cost option.   

Costs for each option are very different, and occur at different times. Don't forget to factor in infrastructure development, administration costs, procurement costs, and maintenance and upkeep costs. For example, installing fueling stations is much more expensive than providing preferred parking spaces with signage.

There are two options available for attaining this credit. Determine the most feasible compliance path for your project early in the process:

Option 1: Provide preferred parking for low-emitting and fuel-efficient vehicles for 5% of total parking capacity or, a discounted parking rate (at least 20%) for low-emitting and fuel-efficient vehicles.
Option 2: Install alternative-fuel stations for 3% of parking capacity.

There are two options available for attaining this credit. Determine the most feasible compliance path for your project early in the process:

Option 1: Provide preferred parking for low-emitting and fuel-efficient vehicles for 5% of total parking capacity and one designated drop-off space for low-emitting and fuel-efficient carpools. 
Option 2: Provide low-emitting and fuel-efficient or alternative-fuel maintenance vehicles and school buses for 20% of the fleet (by fuel consumption or vehicle type). 

Pick the best of the four compliance path options for attaining this credit: