Due to safety concerns, the final 100 cars of the R40A order were re-designed with traditional straight-ends by Sundberg-Ferar and became known unofficially as the "R40M" (M for modified).

After being retired, most R40s and R40As were stripped and sunk into the Atlantic Ocean as artificial reefs, but a pair of R40 slants and several straight-ended R40As have survived.

Located on the upper part of the middle set of windows, the new arrangement originally used a single sign that displayed the service and termini on the outside, and a route diagram on the inside.

In addition, the cab ends of the cars now featured a single roll-sign, located on the opposite side of the driver's cabin, that displaying the route.

This pattern became standard for all subsequent roll-signs, albeit with slight placement and design variations, until the R142 and R142A orders in 1999, which switched to a single red LED sign up front with the route, and the sides signs displaying the current destination and the line all in yellow with LEDs and LCDs, which that became standard for the first “generation” of New Technology Trains.

Moreover, the R40s and slant-ended R40As were the last subway cars to feature distinctive "EXP" (express) and "LOCAL" marker lights on the cab ends, albeit centered.

The more attractive design was intended to beautify the subway and was part of an effort to convince people to abandon their cars for mass-transit.

In addition to the slanted ends, the new cars were to have wider doors and windows, easier-to-read signage, and improved interiors with light colors.

The first incomplete pair of R40s (cars 4350–4351) arrived on TA property in November 1967 for promoting of the Transportation Bond issue on Election Day.

Due to the lack of handholds on the slant-ends, concerns were raised that passengers walking in between cars could fall onto the tracks.

Meanwhile, the director of design at Raymond Loewy claimed that there was to be no passage between subway cars; the doors were to be locked and thus the safety features would have been unneeded.

In November 1968, the NYCTA began modifying the slant-ended fleet at a cost of $400,000 with large grab rails and pantograph gates, which effectively destroyed Loewy's design, but allowed passengers to travel safely between cars.

Since the straight-ended R40As came factory equipped with baloney coiled spring type inter car safety barriers on their blind ends, they did not need such installations that the R42s received.

Pair 4200–4201 was badly damaged in a rear-end accident on the North Channel Bridge on September 12, 1970 and subsequently scrapped.

[2] Lastly, the distinctive "EXP" (express) and "LOCAL" marker lights on the slant-ended cars were also removed.

The full list includes: Media related to R40 (New York City Subway car) at Wikimedia Commons